Future Planetary Exploration

Alternative source of new mission news

2018-12-21T22:00:00.002-08:00

I'm finding the professor gig is keeping me pretty busy, and posts here have become scarce. I still do expect to post irregularly here. You can find many posts of future planetary missions at the NASASpaceflight.com site, where I post fairly regularly. Two recommended forums:

Space science coverage
Mars missions

Discovery 2019 Competition

2018-12-21T21:53:00.000-08:00

NASA recently posted its draft Announcement of Opportunity for its next Discovery competition that will select two missions, one to fly in the mid-2020s and the other in the late 2020s. I am starting to see in scientific conferences missions likely to be proposed (several of which were also proposed but not selected for the last competition that selected the Lucy and Psyche asteroid missions). NASA expects to select up to five finalists for further definition with the final selections from this candidate list.

Mission proposals can target any solar system study, except those that would study the sun or Earth, that, “Ascertain the content, origin, and evolution of the solar system and the potential for life elsewhere.”

Mission costs for the spacecraft, instruments, flight software, and ground systems (the Principal Investigator costs) are capped at $500 million in FY2019 dollars. NASA provides management, the launch, and covers mission operations in addition to the PI costs. These other costs can be substantial. The projected full cost of the Lucy mission is $914-984 million and the Psyche mission is $907-957 million when the PI costs were capped at $450 million in FY2015 dollars.

The PI budget can be adjusted upward by up to $20 million by adding a technology demonstration (see below) or up or down by $10-20M by selecting a less capable or a more capable launch vehicle than the baseline. Instruments, up to approximately one-third of the payload, can be contributed by foreign space agencies or governments outside of the PI cost cap.

The target schedule for the selection and launches of the Discovery missions is:

AO Release Date (target)................February 28, 2019
Proposals due.................................May 31, 2019
Selection of up to 5 finalists............December 20, 2019
Selection of up to 2 final missions...March 31, 2021
1st launch period............................July 1, 2025, through Dec. 31, 2026
2nd launch period...........................July 1, 2028, through Dec. 31, 2029

NASA will select the winning proposals based on three criteria:

• Scientific merit of the proposed investigation (40%)
• Scientific implementation merit and feasibility of the proposed investigation (30%)
• Technical, management, and cost feasibility of the proposed mission implementation (30%)

Proposed missions can use the plutonium-238 MMRTG power systems. However, including these will cost the PI budget $54 million for the first MMRTG and an additional $15 million for the second.

In what I believe is a new opportunity for Discovery proposals, PI’s can propose (or NASA may add), “An Enhancing Technology Demonstration Opportunity (TDO) consists of either PI-team-developed or NASA-developed technologies that may have a TRL of less than 6 [approaching but not yet ready for flight] when proposed, is not required to achieve the Baseline or the Threshold Science Mission, but could enhance the scientific return or reduce cost and complexity of the proposed mission and/or future missions. An Enhancing TDO may be an instrument, investigation, new technology, hardware, or software demonstrated on either the flight system.”

Missions are also expected to, “provide active research opportunities for current or aspiring graduate
or undergraduate students, including advanced high schoolers. SCs may involve students in multiple aspects of a mission spanning scientific formulation; mission planning; systems engineering; design and development of flight hardware; qualification, test and integration; and mission operations and data analysis.”

A Comet or Titan: The Next New Frontiers Mission

2018-04-29T12:06:00.000-07:00

The two concepts contending to be selected as NASA’s next planetary mission have two things in common.

Both would do compelling science.

Both would not begin their scientific missions until the mid-2030s.

Otherwise the two missions could not be more different.

The Comet Astrobiology Exploration Sample Return (CAESAR) mission would return to the comet 67P/Churyumov-Gerasimenko that the Rosetta spacecraft and its lander Philae previously studied. The CAESAR spacecraft essentially would be a high-tech truck that would grab a small sample from the surface and then return it to Earth. Except for some ancillary observations performed by its engineering cameras, the science would begin when the samples are delivered to the exquisitely sophisticated instruments in terrestrial laboratories where they would be analyzed grain-by-grain and isotope-by-isotope.

The Dragonfly mission would return to the surface of Saturn’s moon Titan that is at once both an Earth-like and an utterly alien world. The craft would alternate between flights to new locations and much longer periods as a stationary surface station. Every flight would be a voyage of discovery above a barely known surface. Every landing could provide a new site to explore in depth. Every minute of its potentially many year sojourn at Titan would be spent doing science.

Both missions are finalists in the competition to be NASA’s fourth New Frontiers mission. (Previous selections were the New Horizon’s Pluto-Kuiper belt spacecraft, the Juno Jupiter orbiter, and the OSIRIS-REx asteroid sample return mission.) These are the mid-class missions of NASA’s solar system exploration program that are launched once to twice a decade. NASA’s managers selected these two concepts from a field of twelve proposals (and here).

The CAESAR and Dragonfly missions differ so much because they represent different stages in the progression of exploration. Comets have already had several flyby missions and one orbiter-lander mission. As a result, the top priority among comet specialists is to progress to the next step, sample return. Further exploration isn’t the priority. The lowest risk mission that grabs and brings back the sample is the best mission.

Titan, on the other hand, was studied by the Cassini spacecraft through a multitude of flybys that cumulatively mapped the surface at only low to moderate resolution. (Titan’s atmosphere was also explored by the Huygens probe that descended to the surface, but it carried out only the simplest measurements of surface’s physical properties once it landed.) The next step is to land to study the surface in detail. Titan offers a unique opportunity in the solar system where a thick atmosphere coupled with low gravity allows a science station to relocate itself by flying to new sites. For this world, exploration is the priority.

CAESAR

Comets are deep frozen remnants from the birth of our solar system. They contain relatively unaltered ices and dust from the interstellar cloud from which our solar system formed as well as the processed material that resulted from the earliest steps in the formation of comet-sized bodies. By returning samples to Earth, scientists can determine what materials were available to build the planets. They also can study the earliest chemical pathways that led to creating more complex molecules and the physical processes that accumulated the interstellar material into larger bodies. As one recent scientific paper put it, “comets record chemical evolution in the protoplanetary disk and allow us to unveil the formation history of the organics and volatiles,” while another in the same issue notes that the Rosetta spacecraft found that comet 67P, “revealed a greater variety of molecules than previously identified and indicated that 67P contained both primitive and processed organic entities.”

The CAESAR mission would return to comet 67P/Churyumov-Gerasimenko. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; processing by Giuseppe Conzo

However, instruments that can fit the tight mass, size, and power budgets to be flown on spacecraft are limited in their ability to explore the composition of these materials. The far more sophisticated instruments in Earth-based laboratories – which can be larger than entire spacecraft or even launch vehicles – can study samples grain-by-grain and isotope-by-isotope. The ultimate exploration goal, where technically feasible, for each world is to bring samples back to our world to explore their formation and evolution in depth.

The team proposing the CAESAR mission has laid out a series of hypotheses that would be enabled by examining samples in terrestrial laboratories. Arranged in three themes, the hypotheses address different periods in the formation of the solar system starting with the transition from the interstellar cloud from which the solar system formed. The hypotheses for this theme address questions on what types of unaltered interstellar material were preserved (or not) in 67P. The next theme addresses the nature of the material in the protoplanetary disk and hence the material that would have been available to build the earliest small bodies. Here the key questions focus on whether 67P is a direct descendant of the interstellar medium or also contains high temperature silicates and organics that would have formed close to the early sun and then been blown out to the outer solar system and trapped within the material that formed 67P. The final theme addresses how the current body that is 67P formed from the initial grains of ice and rock available in the earliest solar system, and what role bodies like it played in delivering materials, especially volatiles such as water, to the planets.

The CAESAR mission would be a companion mission to the previously selected, and now in flight, OSIRIS-REx New Frontiers mission. While comets are the oldest frozen remains of the solar system’s formation, several classes of asteroids are considered primitive relics of the earliest formation of solid bodies closer to the sun. The OSIRIS-REx spacecraft will arrive at one of these, 101955 Bennu, later this year. Following a thorough examination of this tiny (~245-meter diameter) body by a battery of remote sensing instruments, the spacecraft will descend, and a robotic arm will grab a sample from the surface to be returned to Earth.

Collecting samples from very small bodies is an engineering challenge because the gravity is too low to enable conventional landings and surface operations. Like the Japanese Hayabusa and OSIRIS-REx asteroid sample return missions, the CAESAR spacecraft would use a touch-and-go sampling mechanism. The spacecraft would slowly descend to the surface with a sample collection system at the end of a long arm below the craft. During the five seconds that the collection system would be in contact with the surface, nitrogen gas would be used to blow the comet’s surface material into a containment system. Because comets contain ices that can freeze into a solid surface, the CAESAR collection system (unlike the OSIRIS-REx system where ices aren’t expected) would have spring loaded ripper tines to break up the surface. The mission’s goal is to collect at least 80 grams of dust and ices, although the collection system can gather several times that if enough loose material is available. After that brief contact, the arm acts as a pogo stick pushing the spacecraft away from the surface and back into space.

The CAESAR spacecraft with its extended arm and sampling mechanism. Credit NASA.

Again, like OSIRIS-REx, following confirmation from instruments that a sample was successfully collected, the containment system with its sample would be placed within a sample return capsule that ultimately would deliver the sample to Earth following a fiery plunge through the atmosphere. However, this capsule and its embedded sample containment system have two major innovations not needed by the OSIRIS-REx mission.

For the CAESAR mission, a key goal is to return both the dusty component and minimally modified samples of the icy volatile material. Once in the sample return capsule, the sample would be gently heated to approximately -30 degrees Celsius to sublimate the volatiles out of the sample. (If -30 sounds chilly, remember that comets are deep frozen relics even following heating by the sun during their passages through the inner solar system.) The sublimated gases would flow to a gas containment system that would be kept at -60 degrees Celsius where they would either refreeze (for example, water) or remain as gases (for example, methane and carbon dioxide) depending on their freezing points. Removing the volatiles from the sample ensures that they don’t chemically modify the solid sample during the return flight to Earth. Keeping them chilled in the gas containment system also minimizes chemical interactions among the volatiles.

The need to preserve a frigid sample system drives a second difference from the OSIRIS-REx return system. During the plunge through the Earth’s atmosphere at the end of the mission, the heat shield would absorb considerable heat that would eventually raise the temperature of the sample. For the rocky material that the OSIRIS-REx mission would return, this isn’t a concern. However, the CAESAR mission would drop the heat shield from the return capsule as soon as the parachute deploys, minimizing any heating of the sample. (This is a technology developed by the Japanese for their Hayabusa asteroid sample return missions, and their space agency would provide the CAESAR return capsule.)

There’s another important difference between the OSIRIS-REx and CAESAR missions. To intelligently select and later interpret samples, scientists need to understand the parent body: What is its shape and interior structure? What processes have shaped it surface? How does the composition vary across the body? The OSIRIS-REx mission is going to a body that has never been visited before. As a result, that spacecraft carries a rich payload of cameras and spectrometers to map the physical surface and its composition. If the mission only completes its survey of the asteroid Bennu but for some reason fails to return its sample to Earth, it would have told us a great deal about how this tiny primitive asteroid came to be.

The CAESAR mission’s target, comet 67P, was previously studied by the Rosetta mission and its partially successful Philae lander. As a result, the CASEAR spacecraft wouldn’t need to carry its own scientific instruments. It does carry narrow- and wide-angle engineering cameras that would be used to remap 67P’s surface, which is likely to have changed during its subsequent perihelion passages from solar heating. (Identifying the changes would be a useful scientific byproduct.) From these images, the science and engineering teams would map the surface in terms of how safely the spacecraft can approach the surface, whether the surface material has physical characteristics compatible with the sampling mechanism, whether the arm can deliver the sample mechanism to the surface, and the intrinsic science value.

Based on maps derived from the Rosetta images, the CAESAR team is currently expecting to take its sample from one of the smooth terrains that appear to consist of material that has slumped there from the rugged terrains that would be unsafe to sample directly. The smooth terrains also likely contain material delivered from the jets that spew a cloud of volatiles and dust in the space around 67P each time it comes close to the sun. Because the rocky and organic materials appear to be nearly uniformly distributed across surface, the key deciding factor on the final sample location likely would be made based on the richness of the volatiles present.

Once the CAESAR spacecraft acquires its sample, it would quickly move away from the comet to wait for the start of its journey back to Earth. If all goes well, the sample would be delivered to the Earth’s surface in the midmorning of November 20, 2038, fourteen years after the mission’s launch. Following the recovery of the sample capsule, the returned gases, ices, and solids would be carefully curated and preserved. The initial analyses on a portion of the sample would be conducted using laboratory instruments that would be 20 years more advanced than those available today. It’s expected that the samples would continue to be analyzed for decades following their arrival on Earth as scientists develop more refined questions and yet more advanced instruments.

Dragonfly

While comet P67 is a well explored world, the surface of Saturn’s moon Titan largely remains a blurry enigma. Thanks to the Cassini orbiter’s many flybys of the moon, we have low- to moderate-resolution maps of the surface that show seas of liquid methane and ethane, extensive dune fields, mountains, a paucity of craters, and river systems. We similarly have low resolution maps of surface composition differences that are frequently ambiguous as to the actual material present. We know that sunlight interacting with the atmosphere creates complex hydrocarbons and nitriles that continuously rain down from the upper atmosphere to the surface. Cassini’s instruments have observed changes in the surface following rains of liquid methane. There’s an interior water ocean that may be in contact with the silicate core that could, like the interior oceans of Europa and Enceladus, be an abode for life.

The Dragonfly rotorcraft shown in its initial landing in a flat area between Titan’s equatorial dunes. Credit: NASA

What we know about the surface becomes the foundation for the fundamental questions that require a return visit. What processes have reshaped the surface, erasing, except in a few terrains, the many craters that should have accumulated? Why hasn’t the rain of hydrocarbons buried the surface over the age of the solar system, and where does new methane come from to replace that lost to the formation of the hydrocarbons? Are there cryovolcanoes that bring liquid water to the surface? What types of pre-biotic chemistries occur on a world rich in hydrocarbons? And is there evidence of life, either that formed on the surface from the interaction of water and the hydrocarbons or carried up from the deep subsurface global ocean? Or is there life based on non-water chemistries?

These questions cannot be answered by landing at any single location on Titan. Fortunately, this moon’s thick atmosphere and low gravity make this the easiest world in the solar system for flight. The team proposing the Dragonfly mission have designed a rotorcraft lander that can fly several tens of kilometers in a single flight to a new site. In an hour or so of flying, the craft might travel further than the Opportunity rover has crawled across the surface of Mars in fourteen years. Over the course of several years at Titan, the craft could explore a variety of terrains hundreds of kilometers apart.

The Dragonfly proposal is possible because of the recent advances in multirotor technology to enable steady flight (think of all the quadcopter hobby drones as inexpensive examples) and autonomous flight. Cassini’s maps of the surface enable scientists to identify interesting locations to visit but are too low resolution (the smallest details are hundreds of meters across) to be useful to for inflight navigation. On each flight, Dragonfly would be given a target location to fly to. During the flight, a combination an inertial measurement unit, radar, and optical navigation would be used to track progress. Once at a landing area, a laser system (lidar for those familiar with the technology) would map the site to find a safe touch down site.

On arrival at Titan, the Dragonfly craft, safely enclosed in its entry capsule, would directly enter the atmosphere. Once the initial descent is completed, the Dragonfly rotorcraft would separate from the capsule and guide itself to its first landing. Much of Titan’s equatorial regions are covered by dunes that crest at 50 to 200 meters separated by flat plains two to four kilometers wide. The craft would use its sensors to guide itself to one of these interdune areas to enable that crucial safe first landing.

The sands themselves are known to be composed of frozen organic particles that likely are material blown in from large areas of the moon’s surface. With its first landings in the dune sea, the Dragonfly lander can explore how far organic chemistry has proceeded on this hydrocarbon rich world. The interdune plains may also contain exposed water ice that is the bedrock of Titan’s surface. Sampling the primordial water ice crust is a high priority to explore the chemistry present when Titan formed and the surface and atmosphere may have been much different than they are today.

Because Titan’s surface is likely rugged at small scales, the Dragonfly team won’t send the craft to land at an unseen location (except for that first landing). Instead, on its first flight following the initial landing, the craft would be sent to scout for a next safe landing site and then would return to the initial (and known to be safe) landing site. On the second flight, the Dragonfly craft would fly past the second known safe landing site to scout a third, and then return to the second site. In this way, the mission would leapfrog from one known safe site to the next, using its sensors to make up for the lack of high resolution orbital imagery.

Beyond the dune seas, Titan has a rich variety of terrains to explore. Life on the Earth is based on organic chemistry enabled by liquid water. The surface of Titan is too cold for liquid water – the water ice is as hard as rock – but impacts would melt the ice, mixing the hydrocarbons with liquid H₂O for as long as tens of thousands of years. Where liquid water and the organic material on the surface mixed, complex pre-biotic chemistry likely occurred, making Titan a natural laboratory to explore the possible origins of life. These sites would provide natural laboratories to explore the resulting pre-biotic chemistry and explore avenues for the origins of life.

Cassini’s data hint at features that may be extensive cryovolcanic flows where water from the interior ocean reached the surface. If the liquid water originated in the deep interior ocean, sampling these areas may allow the Dragonfly instruments to determine the composition of that ocean, including searching for signs of any life that may exist there.

While liquid water on the surface has likely been a rare event, liquid methane plays the role on Titan that water does on Earth. The methane falls as rain, flows through river systems, and ends in lakes and seas. Close to the equator where the Dragonfly craft would roam, it appears that the seas have largely dried up. The evaporation of the seas could have concentrated chemical reactions, and the present dry-to-moist surface would preserve the resulting material for Dragonfly’s instruments to sample. Several areas near the equator have been identified as possible dry sea beds. (The currently-filled methane seas in the north polar region would be in darkness and out of sight of Earth for telecommunication during the Dragonfly mission. Their exploration would need to wait for another mission a decade or so later).

The Dragonfly’s explorations would be tempered by the need to carefully manage its power use. The craft would carry a radioisotope power source that at Titan would supply a constant ~70 Watts of electrical power. (And as importantly, it provides plentiful supply of waste heat to keep the craft warm on the -180-degree Celsius (-290-degree Fahrenheit) surface.) That supply is too low for the major power-hungry activities – flight and returning data to Earth – but is enough to recharge a large battery. Operations would proceed at the pace of each Titan day (around 16 Earth days). During the night, the battery recharges, followed by a daytime flight and a series of science activities and data downlinks. During the long night when Earth is out of sight, the craft would power down many systems to keep its meteorology and seismic instruments powered and permit battery charging. (The Curiosity rover on Mars is similarly power limited. Its radioisotope power source charges a battery that powers driving and many operations. The difference is that days on Mars have a similar length to our own.)

The public information on how far the Dragonfly craft might go in a single flight is somewhat vague – the design is not yet complete and there’s a tradeoff between larger batteries and weight and volume. One article discusses an example battery that could allow up to 60 kilometers flight. It then states that flights would be kept substantially shorter to provide a safety margin. If the average distance between landing sites is 20 kilometers when the goal is to transit distances, then over a five Earth year mission, the craft might fly 1500 to 2000 kilometers. Not all Titan days, though, are likely to be spent with the goal of putting kilometers on the odometer. If the craft finds a cryovolcanic volcano or flow, for example, it may spend many months doing short flights to different locations within the flow. Some Titan days may be spent doing aerial reconnaissance to map the feature. Other Titan days might be spent doing bunny hops between features in a single landing area.

Examples of terrains within a region on Titan. The 5 µm bright areas have been interpreted as dried sea beds. The distance across the more detailed map is approximately 2700 kilometers at the equator. Credit: Dragonfly team.

Rather than thinking of the Dragonfly craft as a global trekker, it seems more apt to think of it as performing the equivalent of the missions of several rovers on Mars. It would be able to transport itself between and within several key landforms within a region of the moon. Choose that region carefully, though, and there’s a rich diversity to explore. Within the black box on the map above lie seas of sand dunes, several features that may be cryovolcanic, possible dried sea beds, and what may be one of the oldest exposed terrains on the surface in the Xanadu highlands with its mountains, river channels, and possible impact craters.

During its flights, a set of cameras would look forward and downward during flights to map the. The Huygens probe showed that surface features can be distinguished in monochrome aerial images, and Dragonfly would have some color imaging capability to discriminate differences in composition. The mission’s operators, though, would need to balance the number of images returned with other demands on the mission’s power supply. The strategy would be to return thumbnails of images, from which the mission team would select a subset to be returned at higher resolution.

After each landing, panoramic cameras would examine the local area while microscopic cameras take close-up images. (Depending on the wavelengths that the cameras can detect, Saturn may be visible in the images in one of the spectral windows in which the atmosphere is transparent.) Once on the surface, a gamma-ray and neutron spectrometer would measure the bulk surface composition to discriminate between, for example, pure water ice, ammonia-rich water ice, and a layer of hydrocarbons.

Several instruments would study meteorology both in flight and on the surface including temperature, wind, and the methane humidity. Two instruments would listen for seismic activity and measure variations in the extremely low frequency electromagnetic field to study the subsurface to the depth of the interior water ocean. Other sensors would record the thermal and electrical properties of the surface immediately around the landed craft.

The mission’s star instrument, however, would be its mass spectrometer. This instrument, derived from similar instruments for the Mars Curiosity and the European ExoMars rovers, would be able to detect the presence of different ices and hydrocarbons at minute levels. By measuring the precise chemistry of ices from different locations, scientists can understand the processes that created them.

This instrument’s sensitivity would make Dragonfly an exciting astrobiology mission. It could, for example, measure tiny amounts of key organic compounds such as amino acids, lipids, and sugars, as well as the chirality of organic molecules. At the minimum, Titan should have a treasure trove of pre-biotic material that scientists would use to explore the chemical pathways leading to the complexity of life. And Titan is a possible abode for life, either as-we-know-it based on water in the deep ocean or novel forms of life based on liquid methane. Proving that life exists at the cellular level likely would be hard, but Dragonfly’s measurements could be the bridge to future, even more sophisticated missions.

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Both CAESAR and Dragonfly would be compelling missions. It is unfortunate that only one will be selected and the next competition is likely to be several years in the future.

Launch for the CEASAR mission would occur in the summer of 2024 and arrive at comet 67P in December 2028. The spacecraft would depart from the comet in late 2033 and return to Earth five years later.

Launch for the Dragonfly mission would occur in 2025 with arrival at Titan in the mid-2030s. Absent a crash or equipment failure, the length of the mission would be dictated by the slow decay of power delivered from its power supply. Eventually it would take two, then three, and then more Titan days to recharge the battery. At some point, power would be too low to enable any flight. Then the craft would become a stationary science station as power gradually fades until it becomes silent likely sometime in the late 2030s or 2040s.

The decision between these two excellent but fundamentally different missions will be made in mid-2019 by NASA’s Associate Administrator for Science. His decision will determine whether the 2030s brings a flowering of science for comets or Titan.

I would like to thank Steve Squyres, principal investigator for the CAESAR proposal, and Elizabeth (Zibi) Turtle and Jason Barnes, PI and deputy PI for the Dragonfly proposal, for their comments on an earlier draft of this story.

Venus Origins Explorer New Frontiers Proposal

2017-10-01T09:55:00.001-07:00

When I wrote my blog post on the New Frontiers mission proposals, I could identify eleven of the twelve proposals. One, though, then had no public trace. Shortly after my piece was published, several people emailed me to tell me that the twelfth proposal was a third Venus mission called the Venus Origins eXplorer (VOX). However, they offered no details on its implementation.

Now the team proposing the mission will present its implementation at an upcoming scientific conference. Their abstract for the talk reveals key facts about the proposal, and it’s a gutsy break with the missions that have been assumed for New Frontiers Venus missions.

NASA's Magellan spacecraft mapped the surface and gravity field of Venus in the early 1990s. The VOX mission would return with a modern suite of instruments to remap the surface and study the lower atmosphere. Credit: NASA/JPL.

To understand the strategy the VOX team is following, it’s useful to look at the history of the Juno Jupiter orbiter mission. Every ten years, the planetary scientific community establishes its priorities for the exploration of the solar system in process known as the Decadal Survey. The 2003 Decadal Survey report called for a Jupiter Polar Orbiter with Probes mission. The orbiter was to study global patterns and the magnetosphere while three atmospheric probes were to examine the composition and deep structure of the atmosphere. Unfortunately, since the Galileo mission with its shallow atmospheric probe, the United States has lost the technology to build probes capable of entering Jupiter’s atmosphere. The team that proposed the Juno mission focused on the desired scientific goals and demonstrated that they could be met with just an orbiter with the right instruments. Based on that well-presented argument, the mission was selected and is now orbiting Jupiter.

The goals for a New Frontiers mission for Venus have assumed an atmospheric probe that would also conduct surface measurements once it landed. The scientific requirements NASA’s managers established for a mission appear tailored for that kind of a mission based on the goals set out by the more recent 2013 Decadal Survey report. For example, the ratio of key gasses and their isotopes can only be made by a probe that enters and directly samples the atmosphere. With those measurements, other questions such as past hydrologic cycles and the existence of now lost oceans can be addressed. During its descent the probe could measure the properties of the atmosphere, its clouds, and its winds at different altitudes. Measurements of the atmosphere at the surface could address the weathering environment of the crust. Chemical analysis of the soils and rocks at the landing site could provide insight into the physics of and chemistry of the crust.

Two of the proposed New Frontiers missions would fly either one or two entry probe-landers to address these questions. (You can see summaries of these at this blog post.)

The VOX proposal takes an entirely different approach. As the abstract states, “At the time of the Decadal Survey the ability to map mineralogy from orbit and present-day radar techniques to detect active [surface] deformation were not fully appreciated. VOX leverages these methods and in-situ noble gases to answer [the key] New Frontiers science objectives.”

The VOX mission would deploy a small, simple atmospheric probe to make the measurements of the key gases and isotopes. The rest of the measurements would be made from instruments on an orbiter, much as the Juno mission uses orbital measurements to replace measurements from atmospheric probes. (The composition measurements for Jupiter that could only be made from within an atmosphere had already been made by the Galileo mission’s atmospheric probe.)

The key elements of the VOX proposal closely resemble the VERITAS mission that was a finalist for the last Discovery program mission but not selected (losing out to the Lucy and Psyche asteroid missions). The principal investigator for VERITAS and VOX are the same, Suzanne Smrekar at the Jet Propulsion laboratory. The core of the VERITAS proposal was an orbiter that would carry a modern radar instrument to remap Venus and a spectrometer to measure the surface composition and study key aspects of the atmosphere. If selected, the VERITAS mission team was considering proposing a small atmospheric probe call Cupid’s Arrow to toe-dip into the atmosphere to make key composition measurements. A version of that probe now called the Atmospheric Sample Vehicle (ASV) would be included in the VOX mission.

The VOX orbiter would use three instruments to globally study Venus:

A radar instrument would image the surface at 15- to 30-meter resolution, map elevations to refine topography measurements, and search for minute changes in surface elevations to look for evidence of current volcanic or tectonic activity. The improvements in resolution for each of these would be one to two orders of magnitude better than those made by the Magellan orbiter in the 1990s.

The orbiter’s radio signal would be used to map the gravity field at much higher resolution than the Magellan mission to study the interior structure of the planet

The Venus Emissivity Mapper (VEM) would use spectral bands in five near-infrared wavelengths where the atmosphere is transparent to map the surface composition. Measurements in additional bands would study cloud structure and the presence of water vapor in the lowermost atmosphere.

These images, derived from radar imaging of Hawaii, show the improvement in resolution possible with modern radar systems compared to the data returned by the Magellan mission. This image is from a poster describing a 2012 JPL VERITAS mission that was proposed for the NASA Discovery program. The VOX mission would carry the same radar instrument. Credit: JPL

These figures show the improvement in topographic resolution possible with a modern radar instrument using data from Iceland. The top image shows the equivalent Magellan resolution and the bottom image shows simulated resolution possible from a new Venus radar mission. Credit: Decadal Survey White Paper, NASA

The Venus Express mission carried out the first mapping of Venus’ surface using thermal emissions. The VOX mission's Thermal Emissity Mapper instrument would create better composition maps than the Venus Express instrument. Red-orange colors in this Venus Express image of Venus’ Idunn Mons volcanic peak indicate warmer areas suggesting different surface compositions and younger ages than surrounding material. Credit: ESA

The ASV would be a small probe released from the orbiter. The probe would enter and briefly traverse the upper atmosphere where it would collect a small sample of the gasses present before its momentum carries it back into space. Once back above the atmosphere, a miniaturized mass spectrometer would measure the composition of key gasses and their isotopes. By only toe-dipping into the atmosphere, the probe doesn’t need protection from the crushing pressures and extremely high heat on the surface that the atmospheric probes of the other New Frontiers Venus proposals require.

The VOX mission's Atmospheric Sample Vehicle would be based on the Cupid Arrow probe concept. Credit: NASA/JPL.

While the VOX mission is in competition with the two Venus entry probe-lander proposals (and nine other proposals for other solar system destinations), in many ways it is a compliment to those two missions. Within the column of air in which they descend and in a square meter or so at their landing sites, the two proposed entry probe-lander missions would make much more detailed measurements than VOX’s radar and VEM instruments would from orbit for the same location.

The VOX spacecraft’s instruments, however, would make those measurements over the entire planet over at least three years (and possibly much longer in an extended mission). The VEM instrument, for example, could look at the surface of every volcano on Venus searching for the presence of minerals suggesting recent lava flows. The radar images could show whether the features on the surface are consistent with new flows. Radar interferometric measurements could look for small surface deformations that could reflect surface movement from earthquakes associated with eruptions or swelling from underground lava movement. VEM measurements of the atmosphere could look for changes in water vapor associated with volcanic outgassing. And the gravity field measurements would tie each volcano to the interior structure below the surface.

The VOX mission would make comparable studies for all the surface types on Venus as well as monitor the lower atmosphere. Perhaps most important of these would be observations of the tessera, which are continent-sized highlands that likely are the oldest surviving surfaces on the planet. For these, the synergy of composition measurements, surface imaging, and interior structure measurements could reveal key aspects of the earliest history of Venus including the role of liquid water and other volatiles in the then cooler times.

In one set of measurements, the VOX and the two Venus entry probe-lander missions are in direct competition. In much the same way as strata of rock record geologic history, the presence and abundance of key gasses and their isotopes record the origin and evolution of the atmosphere. Because the Venusian atmosphere is in contact with the surface, it also records key geological events. Measurements of xenon and its isotopes, which have yet to be made at Venus, for example, would resolve key questions about the origins of the atmosphere. Xenon measurements also would reveal the total amount of degassing from the planet’s interior, which reflects the cumulative volcanic activity. Similarly, a long-lost ocean at Venus would be reflected in the ratio of hydrogen isotopes.

The US Pioneer Venus and Soviet Venera entry probe and landers carried now-antiquated mass spectrometers that could not make key composition measurements such as the isotope ratios of xenon. The VOX mission’s atmospheric probe would deliver a modern mass spectrometer to Venus that would answer the key first order atmospheric composition questions. The other two proposed Venus missions would carry much more sophisticated instruments that could also address second and third order questions. By descending all the way to the surface, the probes on these other missions would also study changes in composition at different layers of the atmosphere and look for compounds that reflect the current weathering at the surface.

(As a side note, I’ve been following proposals for missions to explore the solar system for several decades now. Cupid’s Arrow, and its incarnation as VOX’s ASV, is in my opinion one of the cleverest solutions I’ve seen to addressing a key set of planetary science questions at a fraction of the cost of much more capable entry probes like those that would be the core of the other two Venus proposals.)

To understand Venus, eventually it’s not a question of a VOX-like mission versus entry probe-lander missions. Their capabilities are complimentary – in depth at one or a few locations versus broader measurements across the entire globe across a number of years. The interpretations of measurements from orbit, especially those of composition, would greatly benefit from ground truth measurements on the surface. Eventually, we need both types of missions to fly. (And there’s also an entire branch of Venus science focused on global atmospheric studies from orbit that neither of these types of mission addresses.)

In the last New Frontiers competition, a Venus entry probe-lander was a finalist but lost out the OSIRIS-REx mission now inflight to return a sample from the asteroid Bennu. For the current Frontiers competition, NASA will select just one mission from among three proposals for Venus, one to return samples from the moon, three to return samples from a comet, and four to study Saturn or its moons. It’s a tough field. By the end of this year, we’ll learn whether VOX is selected as a finalist in the current competition with the final selection planned for 2019.

Appendix: Here is the full list of studies proposed for the VOX mission from the conference abstract:

1. Atmospheric physics/chemistry: noble gases and isotopes to constrain atmospheric sources, escape processes, and integrated volcanic outgassing; global search for current volcanically outgassed water.
2. Past hydrological cycles: global tessera composition to determine the role of volatiles in crustal formation.
3. Crustal physics/chemistry: global crustal mineralogy/chemistry, tectonic processes, heat flow, resolve the catastrophic vs. equilibrium resurfacing debate, active geologic processes and possible crustal recycling.
4. Crustal weathering: surface-atmosphere weathering reactions from redox state and the chemical equilibrium of the near-surface atmosphere.
5. Atmospheric properties/winds: map cloud particle modes and their temporal variations, and track cloud-level winds in the polar vortices.
6. Surface-atmosphere interactions: chemical reactions from mineralogy; weathering state between new, recent and older flows; possible volcanically outgassed water.

Articles, September 3, 2017

2017-09-03T15:19:00.000-07:00

The last two weeks have seen a number of articles and press releases on future planetary exploration. The big news was that NASA’s managers are proposing a fast track Mars sample return mission for the mid-2020s. Numerous articles were written; I’ve listed several that I thought were among the best I saw.

You might also want to check out Leonard David’s story, Beating Curiosity, on the technical enhancements that will enable the Mars 2020 rover mission.

For fans of Titan exploration, there’s now a website for the proposed Dragonfly rotocraft and an article on the proposed Oceanus orbiter.

Several other articles discuss other plans and proposals to explore the planets.

Mars

Beating Curiosity

By Leonard David|September 2017

A future comes into focus for the Mars Exploration Program

Casey Dreier • August 31, 2017

NASA studies mission to return samples from Mars by end of 2020s

August 28, 2017 Stephen Clark

NASA considers kicking Mars sample return into high gear

Jason Davis • August 28, 2017

NASA's Next Mars Mission to Investigate Interior of Red Planet

Jet Propulsion Laboratory

Titan

Proposed Orbiter Could Probe the Ocean Beneath Saturn's Moon Titan

By Nola Taylor Redd, August 24th, 2017

APL proposes Dragonfly mission to explore potential habitable sites on Saturn's largest moon

Dragonfly website

Presentation on Dragonfly (YouTube)

Venus

A clockwork rover for Venus

NASA studies CubeSat mission to solve Venusian mystery

Rounding out the field

James Webb Telescope will study our solar system's 'ocean worlds'

August 24, 2017 by Eric Villard

CubeSats: faster and cheaper, but are they better?

by Jeff Foust

Articles, August 29. 2017

2017-08-19T20:36:00.002-07:00

Press Releases

Mars 2020 mission to use smart methods to seek signs of past life

NASA studies CubeSat mission to solve Venusian mystery

NASA Studies Tethered CubeSat Mission to Study Lunar Swirls

Space.com

Mars Sample Return: Scientists Debate How to Bring Red Planet Rocks to Earth

By Leonard David

Science

Missions to probe exoplanets, galaxies, and cosmic inflation vie for $250 million NASA slot

By Daniel Clery Aug. 16, 2017

The Space Review

CubeSats: faster and cheaper, but are they better?

By Jeff Foust

Space News

Beyond HAL: How artificial intelligence is changing space systems

by Debra Werner — August 15, 2017

China Spaceflight

Chang'e VI: plans to be launched around Wenchang from around 2020 to achieve the return of the lunar poles

Unless you read Chinese, you’ll need a translation program such as Google translate

Proposed New Frontiers Missions

2017-08-04T19:42:00.000-07:00

NASA’s managers are in the processing selecting the agency's next planetary mission from a field of twelve competitors. This fourth mission in the New Frontiers program will follow in the footsteps of the three missions in this program that have already launched: The New Horizons Pluto spacecraft, the Juno Jupiter orbiter, and the OSIRIS-REx asteroid sample return mission.

By law, NASA’s managers cannot reveal information on the proposals submitted to protect the proprietary ideas of the proposing teams. However, the proposing teams often will disclose some information on their proposed missions at meetings and conferences. For the past year, I’ve been collecting their presentations and abstracts and can describe nine of the twelve missions in this article. (For two other proposals, I know only their target, and the twelfth proposal remains a mystery.)

New Frontiers missions are a key component of NASA's program to explore the solar system. Like Goldilocks's bears, NASA's planetary missions come in three sizes. At the low end, costing $600-700 million, are the more frequent Discovery missions that address tightly-focused questions on (for planetary exploration) tight budgets. NASA plans to fly several Discovery missions in the coming decade. At the high end, typically costing greater than $2 billion, are the Flagship missions that host a wide range of instruments for in-depth studies. NASA typically flies just one Flagship mission a decade, although the next decade will see two launches, the Mars 2020 rover and the Europa Clipper.

However, there are a range of studies that the scientific community deems essential to understanding the solar system that can't fit within the Discovery program, but don't require a Flagship mission. This is the role of the New Frontiers program with missions costing somewhere around $1 billion with a planned flight rate of two per decade.

The list of possible missions for the New Frontiers program are pre-selected by a panel of scientists once a decade in a process that sets exploration priorities known as the Decadal Survey. For this current competition, NASA’s managers added two additional targets, Saturn’s moons Enceladus and Titan.

The New Frontiers missions that have been publicly described include proposals that emphasize composition measurements to address the formation and evolution of the solar system (the CONDOR and CORSAIR comet sample return and the SPRITE Saturn probe proposals) or the formation and evolution of terrestrial worlds (the VISAGE and VICI Venus atmospheric probe-landers and the lunar Moonrise sample return proposals). The ELF Enceladus mission, the Titan Oceanus orbiter, and the Titan Dragonfly rotocraft would explore their target worlds for habitability and signs of life. The latter two missions also would continue the broader exploration of Titan.

The selection of any of these missions would significantly advance planetary science. NASA will choose among them based on two criteria: Would the proposed mission likely meet its scientific goals? How feasible is the mission technically within the budget cap of $850 million for the spacecraft, instruments, and mission operations? (Additional costs such as launch would raise the final cost to around $1 billion.) The review process is thorough and daunting; any weaknesses on either criterion can disqualify a proposal or cause it to be ranked poorly compared to its competitors.

NASA expects to select two to three of these proposed missions this fall for further definition and review. The winning mission will be chosen from this short list by mid-2019 for launch no later than 2025. Travel time to the selected destination could be as short as a few days or as long as twelve years.

Dates for key events in the proposed New Frontiers missions. *Proposing teams have not given dates for the Moonrise and Dragonfly Titan missions. Dates shown are my best estimates based on the requirement to launch by the end of 2025 and flight times to reach destinations.

Venus In Situ Explorer

Two of the proposed New Frontiers missions would return to land on Venus. Image from the Soviet Venera 13 lander. Credit: Brown University / Vernadsky Institute / Olivier de Goursac

Two key questions have led the two Decadal Surveys (published in 2002 and 2012) to include a mission to directly sample the atmosphere and surface of Venus. The first is how terrestrial planets formed and the second is how Venus evolved from a world that likely had a moderate climate with oceans to its present hellish conditions. As the 2002 Decadal Survey report notes, “Venus and Earth may have had very similar surface conditions early in their histories, but Venus’s subsequent evolution was different from Earth’s, developing an environment unsuitable for life. However, Venus is still a dynamic world with active geochemical cycles and non-equilibrium environments in the clouds and near surface that are not understood.”

To meet the goals of this mission, a spacecraft would need to conduct two sets of measurements. First, it would make detailed measurements of the atmosphere’s composition during its descent to and on the surface. The mixture of gases in a planet’s atmosphere, especially the ratios of isotopes of key elements, provides both a fossil record of that world’s formation and evolution and insights into current processes such as surface weathering and volcanic activity. Once on the surface, the craft would measure the composition of the rocks and soils to allow scientists to reconstruct the processes that initially formed that location and subsequently modified it.

Soviet and American probes in the 1970s and 1980s performed both sets of measurements, but the then available technology lacked the precision to answer key questions. The two proposed New Frontiers missions would each carry the latest generation of instruments that would provide far more detailed measurements than their predecessors.

In the last New Frontiers competition, a Venus proposal led by Larry Esposito of the University of Colorado was a finalist but wasn’t selected to fly (losing out to the OSIRIS-REx mission). Esposito is again leading a team for the current competition, proposing the Venus In Situ Atmospheric and Geochemical Explorer (VISAGE) mission. During the atmospheric descent, the VISAGE craft would use a mass spectrometer to measure atmospheric composition and a suite of instruments to measure the temperature, pressure, and wind profiles. Mass spectrometers are the workhorse instrument for atmospheric composition measurements, and you’ll notice that several of the proposed New Frontiers missions would carry one or more. Mass spectrometers “weigh” the material they sample and the distribution of those weights reveal the composition of the atmospheric gases. (Versions also exist that can be used for composition studies of ice and dust particles.)

Once on the surface, a drill on the VISAGE lander would retrieve soil samples from “two depths” and deliver them inside the spacecraft. There, one or more instruments could operate at moderate temperatures to make detailed elemental and mineralogical composition measurements. (The X-ray fluorescence instrument would almost certainly be entirely inside the craft’s pressure vessel. The mission’s visible and near-infrared spectrometer likely also would view the samples inside the craft, but might also examine composition outside the craft through a window.) Cameras to image the surface during the descent and take panoramas after landing would round out the instrument package. Because of the extreme temperatures on the surface, the craft would survive to make measurements for only several hours.

The Venus In situ Composition Investigations (VICI) mission led by Lori Glaze of NASA’s Goddard Spaceflight Center would address the same overalls goals but with a different emphasis. While the VISAGE mission would accept the complexity of a drill and air lock to bring samples inside the craft for improved soil measurements, the VICI mission would carry a second instrument (a tunable laser spectrometer) in addition to the mass spectrometer for improved atmospheric composition measurements. Tunable laser spectrometers complement mass spectrometers by being able to precisely measure specific isotope ratios and the abundance of key gases such as water, carbon dioxide, and sulfur dioxide.

On the surface, another instrument uses Raman and laser-induced breakdown spectroscopy to study the composition of the rocks and soil. This instrument would fire laser pulses through a window to measure composition at multiple locations near the craft. At lower power but higher wavelength, the laser enables Raman spectroscopy for mineralogical measurements, and at higher power but a lower wavelength the laser melts a tiny portion of the soil or rock for elemental measurements.

Additional VICI instruments would provide further surface measurements. A gamma-ray spectrometer would sense the presence of trace amounts of radioactive elements in the soil through the hull to characterize bulk composition. Like the VISAGE mission, the VICI mission would image the surface during its descent, but there’s no mention of a camera to take panoramic images once on the ground.

The conference abstract describing the VISAGE mission doesn’t mention where on Venus it would land. (In the previous New Frontiers competition, Esposito’s proposed mission would have landed on what is believed to be relatively fresh lava flows.) The VICI mission would target the continent-size tessera highlands that are believed to be the oldest surviving surfaces on the planet. And while the VISAGE mission apparently would deliver a single lander, the VICI mission would deliver two landers.

Lunar South Pole-Aitken Basin Sample Return

The Moonrise lander and ascent vehicle concept from the last New Frontiers competition. Credit: JPL and the Moonrise team

Sample return missions are the ultimate composition-focused missions. Their effective instrument suite for studying the elements and minerals in their returned samples includes all the instruments currently in terrestrial laboratories plus many yet to be developed. Some of the experiments on those instruments likely will be performed by scientists not yet born. The Apollo lunar samples continue to be analyzed 45 years after the last was collected.

No spacecraft could hope to carry instruments that can match the capabilities of the best instruments on Earth. As a result, sample return is often viewed as the ultimate goal of planetary science after the missions of exploration have told us enough about a world or class of worlds to ask detailed, targeted questions. In addition to the lunar and comet sample return missions proposed for this New Frontiers completion, there have been three missions launched to return samples from asteroids, Japan plans to return samples from the Martian moon Phobos, and both the United States and China are working toward returning samples from Mars.

In the case of the moon, we have samples from a number of locations from the American Apollo and Soviet unmanned missions. However, answering many of the specific questions that remain about the moon require samples from carefully selected new locations. This is driving the Chinese lunar sample return mission planned for the next year and the proposed Moonrise New Frontiers mission.

Over four billion years ago, an impact on the early moon excavated the largest crater in the solar system creating the South Pole-Aitken Basin. The impact exposed buried layers within the crust and appears to have dug into the mantle below. Later volcanic eruptions occurred over portions of the basin creating small mare. Subsequent impacts are believed to have spread material that resulted from these events across the basin. A kilogram or two of soil (technically, regolith) from this basin should include samples from across this basin that would record how the moon formed and the role of cataclysmic impacts in the history of the terrestrial planets.

The Moonrise lander would touch down within the basin. Its robotic arm then would sieve the surface to collect thousands of tiny (3-20 millimeters) rock fragments because those are what are needed to determine ages and to identify deep-seated materials excavated by the impact. A small bulk sample of the regolith would also be collected. Each of these rock fragments carries the story of its creation in its composition.

An ascent vehicle would return these samples to Earth where each rock fragment can be analyzed in detail. Scientists would be able to place the revealed history of each fragment in the context of the evolution of the moon and the evolution of the Solar System in its first 500 million years using the extensive remote sensing data collected by lunar orbiters and samples from other sites.

In the last two New Frontiers competitions, the Moonrise mission was a finalist for both.

Comet Surface Sample Return

The CONDOR mission would return to comet 67P/Churyumov-Gerasimenko (shown here) to collect two samples for study in terrestrial laboratories. The CORSAIR mission would return studies from a comet, 88P/Howell, that has never been visited by a spacecraft. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; processing by Giuseppe Conzo

Because they spent almost their entire history in the deep outer solar system, comets likely preserve ices and organic materials that have undergone little modification over the eons. Scientists are particularly interested in studying the organic material to better understand the processes that created them and to understand what organic material were possibly delivered to the early Earth. Comets are also rich in dust particles that each can tell a story about the materials from which the sun’s rocky worlds formed. The Stardust mission collected hundreds of dust particles during a high-speed encounter with a comet. However, the collection process necessarily degraded the samples and no ices were collected. To fully understand the history recorded in comets, scientists have made returning minimally-altered samples from a comet their top priority for future comet studies.

The proposed COmet Nucleus Dust and Organics Return (CONDOR) mission would collect up to two samples of material from the surface of comet 67P/Churyumov-Gerasimenko, each of which would represent at least 50 grams in mass. The samples would be collected during brief and gentle touch-and-grabs that would cause little or no modification to the comet material. To get material that would be as least altered as possible by the sun’s heat, the samples would include material from up to 15 centimeters below the surface. After collection, the samples would be maintained at less than -20 degrees Celsius during the return trip and refrigerated at -80 degrees Celsius at NASA’s curation facility to prevent alteration of the samples. For materials such as hydrogen cyanide and carbon dioxide that would sublimate at these temperatures, the sample container will trap the gases from these ices for study on Earth.

Many of you likely recognize that the target comet for this mission, P67, is the same one examined in depth by the Rosetta mission. By returning to this richly-studied comet, scientists will be able to understand the samples acquired within the context of the entire body. The CONDOR spacecraft also will use its camera and measurements of the gravity field to study how P67 has changed during its passes through the inner solar system since the end of the Rosetta mission.

A second comet mission, the COmet Rendezvous, Sample Acquisition, Investigation, and Return (CORSAIR) mission would sample a comet, 88P/Howell, that has never been visited by a spacecraft. This creates the opportunity to explore a new comet in-depth. Where the CONDOR spacecraft would carry just two instruments (with its radio system for gravity studies an effective third instrument), the CORSAIR spacecraft would carry five instruments to measure the composition of the gases and dust released by the comet and to remotely image and study the surface (plus the radio system) for 10 months. Two samples from at least 10 cm below the surface would be collected using a harpoon system along with nine collections of dust gathered from the coma. The samples would not be kept refrigerated; instead, “any volatile ices that are collected are sublimated from the samples and chemically characterized before return” by the instruments on the spacecraft’s mass spectrometer instrument.

There is reportedly a third comet sample return proposal led by Stephen Squyres who has also led the Mars Spirit and Opportunity rover missions.

Trojan Tour and Rendezvous

The Trojan asteroids share Jupiter’s orbit around the sun and are believed to have originated from a range of locations in the early solar system. For this reason, the scientific community has prioritized a mission to study several of these worlds and orbit at least one to learn about their origins and how they shifted position as the solar system formed.

I have not found any information on New Frontiers proposals to study them. The selection of a simpler flyby mission, Lucy, last year to study these worlds may have led potential proposers to conclude that NASA is unlikely to select two Trojan missions back to back.

Saturn Atmospheric Probe

For over a decade, the Cassini spacecraft has observed Saturn’s atmosphere to study its composition and weather. Although remote sensing is invaluable for studying and understanding a planet’s atmosphere, there are certain very key measurements that remote sensing spacecraft are not capable of providing. In particular, noble gases that carry the signature of the epoch, location, and conditions of planetary formation are undetectable from outside the atmosphere. So are the details of many atmospheric processes including the detailed thermal structure and stability of the atmosphere, the deep cloud structures, and the winds.

The Saturn PRobe Interior and aTmosphere Explorer (SPRITE) mission would deliver a probe to Saturn’s atmosphere. As with the proposed Venus missions, scientists have many questions about Saturn’s formation and evolution that can only be answered by directly measuring the precise composition of its atmosphere with a descent probe. Among those questions are where in the early solar system Saturn formed and what role it played in the possible migration of the giant planets following their formation - first inward and then outward to their present locations. Measurements of the helium abundance could resolve a mystery of why Saturn is much warmer today than simple models of its evolution suggest it should be. A rain of helium deep in the deep atmosphere could be the explanation, in which case helium abundance should be depleted in the upper atmosphere where the probe can make its studies. For these measurements, the SPRITE probe, like the proposed VICI Venus probe, would carry both a mass spectrometer and a tunable laser spectrometer.

Another set of questions for the SPRITE probe revolve around the meteorology of the upper atmosphere. During its approximately 90-minute descent, SPRITE would measure thermal structure: temperature vs. pressure, and the change in Saturn’s wind from the cloud tops to the deeper atmosphere. SPRITE would also determine the locations and compositions of Saturn’s different cloud decks. Together these measurements will extend Cassini’s remote measurements of Saturn’s meteorology below the level of the highest cloud tops. Prior to entry, a camera on the SPRITE carrier-relay spacecraft would remotely image the atmosphere – both near the probe entry point and globally - so that the probe’s measurements can be understood in their global context and connected back to prior missions equipped with only remote sensing instruments.

Mission timeline for the proposed SPRITE mission to deliver a probe into the atmosphere of Saturn. Credit: SPRITE team/JPL/NASA.

Ocean Worlds

Saturn’s moons Enceladus and Titan have two proposed missions between them, although for one Enceladus mission, I have found only its name, Enceladus Life Signatures and Habitability (ELSAH). The proposers for the other mission, the Enceladus Life Finder (ELF), on the other hand, have provided considerable information their concept. The Cassini mission discovered that this moon is venting material from its internal ocean. Extensive studies of the plumes suggest that this world may have the conditions needed to host life. Cassini’s now-vintage 1990s era instruments, though, left key questions unanswered. Because the Cassini spacecraft performed extensive studies of Enceladus, the ELF spacecraft could focus its studies on what is perhaps the biggest question of all, is there life elsewhere in the universe?

The ELF spacecraft would enter Saturn orbit and repeatedly fly through this moon’s plumes to determine whether its oceans have the conditions needed to be habitable and whether there are complex organic molecules suggesting pre-biotic chemistry or possibly life. The spacecraft would carry three mass spectrometers to study the composition of the gases and ice and dust particles in the plumes. The measurements from these instruments would be far more sensitive than their counterparts on the Cassini spacecraft allowing the mission to address subtle questions of habitability and life. A camera will also take what the mission’s principle investigator, Jonathan Lunine of Cornell University, says will be spectacular images.

The ELF mission would make ten passes through the plumes of Enceladus to investigate that moon’s habitability and search for signs of life. Credit: ELF team/JPL/NASA.

The two proposed Titan missions would have more wide-ranging goals than any of the other New Frontiers proposals. Both seek to explore Titan as a diverse world.

The Oceanus mission would target the ocean world Titan first through a series of flybys and then from two years in orbit. The spacecraft would explore the creation of complex organic molecules by skimming through the upper atmosphere and measuring the composition using a mass spectrometer that has an order of magnitude greater sensitivity, mass resolution, and mass range than the one the Cassini spacecraft carries. The principle investigator for this proposal, Christophe Sotin with the Jet Propulsion Laboratory, wrote me, “What I find fascinating is that both early Earth and Titan have methane in the upper atmosphere. We have very little information about what happened on Earth as life was emerging. Observing Titan is a window to early Earth to understand what kind of organic chemistry happened there and whether it played a key role in the evolution of life 3.5 billion years ago.” These molecules high in the atmosphere that the Oceanus spacecraft would measure eventually drift to the surface to create organic-rich landscapes.

The spacecraft also would use a camera that observes the surface through the hazy methane-rich atmosphere in three infrared bandwidths to map the distribution of the organics that fall to the surface to understand where they accumulate, how they are transported across the surface, and where they have been eroded. Scientists also would use the camera to map the variability of water ice exposed on the surface. A radar instrument and gravity studies would be used together to understand the structure of the crust and deep interior including the characteristics of the salty water ocean that lies beneath the crust.

Scientists have two key questions regarding that ocean. Is it in contact with the rocky core of the moon? If so, then key silicate elements needed to support life would be available, as they are believed to be at Europa and Enceladus. And, are the rich deposits of organics and the liquid water brought into contact through processes such as water volcanism or deep impact cratering? If complex organics, water, and silicates are found to mix, the case for Titan as a possible abode for life would be strong.

As a side note, both the ELF and Oceanus spacecraft would use solar arrays to generate their power. Just a few years ago, it was assumed that any mission to the Saturn system would require radioisotope generators for power. Advances in using solar cells together with designs for very large arrays reduces both the cost and complexity of exploring these moons from orbit.

The Oceanus spacecraft would map large portions of Titan’s surface in three infrared bands at much higher resolution than the Cassini spacecraft. From its orbit about the moon, the spacecraft will be able to image the surface at 25 meter resolution, about four times higher resolution than in the image from the Huygens probe (bottom left). Credit: Oceanus team/JPL/NASA

The second proposed Titan mission may be the most audacious mission that I believe I have ever seen proposed. This moon’s thick atmosphere and low gravity make it the easiest location in the solar system in which to fly. Recent advances in robotic flight make it possible for a craft to autonomously fly and land without direct control. The proposers of the Dragonfly mission combine these two facts to propose a rotocraft that would repeatedly fly up to tens of kilometers between landing sites. Imagine if the Mars rovers had been able to study and sample locations along a traverse hundreds or thousands of kilometers long instead of the tens of kilometers they have been able to do. The Dragonfly mission would directly explore both the habitability of Titan and search for complex organic molecules that could help us understand how life can arise. It can also search for chemical signs of life on this moon.

The Dragonfly science would be split between flight and landing. While flying, it would remotely study the surface below, sample the atmospheric composition, and profile the vertical structure of the air. The craft could not continuously fly – it needs to recharge batteries from a radioisotope generator during landings to store enough energy for the next flight. At each landing site, it would study the composition of the organics and ices using both a mass spectrometer and a neutron-activated gamma-ray spectrometer. Titan's day is 16 Earth-days long, so the operations timescale is relaxed and there's plenty of time to make measurements as well as recharging. Most of the time is spent on the ground, and in addition to the compositional measurements Dragonfly would use meteorological and seismic instruments to study Titan's atmosphere and interior.

The Dragonfly rotocraft could visit a diversity of terrains event within a single region of Titan. From both its remote and surface observations, the mission would be able to study a variety of geological settings including sites with exposed water ice. Credit: Dragonfly team/John Hopkins Applied Physics Laboratory

News from the past week (July 30, 2017)

2017-07-30T11:36:00.000-07:00

The Senate Makes Its Move: Nearly $200M less for NASA in 2018

Casey Dreier • July 28, 2017

The proposed $19.5 billion would be less than the agency received in 2017, and substantially less than that proposed by the House for the coming year.

China’s quest to become a space science superpower

With major spaceflight milestones behind it, China is working to build an international reputation for space science.

Daniel Marín publishes in Spanish, but Google Translate (and presumably other translators) do a good job of translating into English.

Destiny Plus, a Japanese probe to study the asteroid Phaeton

DART, the NASA probe that will hit a nearby asteroid

Introducing JUICE—the Jupiter Icy Moons Explorer

New Approach for the Blog

2017-07-20T09:25:00.001-07:00

When I started this blog almost a decade ago, there wasn't another site that regularly focused on future planetary exploration. That has since changed, especially with regular postings by Jason Davis at the Planetary Society. At the same time, since I have become a professor, my time is more constrained.

With these changes, I plan to make changes to this blog. First, I will do a weekly posting with links to good articles and blog posts on issues relevant to future planetary exploration. I intend for this to be similar to the excellent Ed's Up weekly collection of excellent news writing (you can subscribe at https://tinyletter.com/edyong209), except that I will post mine here rather than it being an email newsletter.

I also plan to continue to write in-depth analyses about once a month (see the previous post on missions to Uranus and Neptune as an example). Right now, I'm working on a story about what we know about the missions proposed for the current New Frontiers competition. There's good information available on about half of them.

In the weekly updates, I may also write short updates of my own. This week, easily the biggest news is the cancellation of Space X's Red Dragon lander. The company make many claims about this lander (see, for example, here and here). I'm not surprised to see it cancelled. Developing a spacecraft that can land on rockets reliably is hard. NASA, which ultimately funds the development through its contracts with Space X, was skeptical about using this system to land astronauts. Without the terrestrial version, there isn't a Martian version. I recommend Eric Berger's story linked below for more background.

The first full summary of stories published on future planetary exploration will come next week. In the meantime, here's a link to three good stories from the past week.

Congress gives NASA's planetary science division some love (and a Mars orbiter)

Jason Davis • July 19, 2017

The House of Representatives proposed $2.1 billion for NASA's planetary science budget, which would be an all-time high. Part of the increase would be used to start work on a new reconnaissance and communications orbiter.

Back to Mercury! Europe and Japan's BepiColombo mission moves closer to launch

Jason Davis • July 14, 2017

Next year, a pair of probes head to Mercury to answer outstanding questions about our innermost planet, as well as the formation of the solar system.

SpaceX appears to have pulled the plug on its Red Dragon plans

Eric Berger - 7/19/2017, 12:20 PM

How We Would Explore Uranus or Neptune

2017-06-24T10:05:00.001-07:00

One fact dominates the planning for any mission to Uranus or Neptune. They lie far from the sun. Reaching one of these worlds takes so long that by the standards of almost any other mission, the spacecraft is already old before it would begin its observations of its target world. The Juno spacecraft took five years to reach Jupiter and the Cassini spacecraft took almost seven to reach Saturn. A mission to orbit Uranus, by contrast, could take twelve years just to reach its destination, with a launch in May 2031 and arriving at Uranus in May 2043.

As a result, each of these worlds has been visited only once by the 1970s-vintage Voyager 2 spacecraft that performed hectic observations during brief flybys in the mid- and late-1980s. The paucity of information on these two planets has left blank chapters in our understanding of the solar system. The planetary science community wants to return with a spacecraft that stays for in-depth observations and carries modern instruments. Toward that end, a NASA chartered team of scientists and engineers published a report this month outline options for returning to these worlds.

Uranus. Credit: Lawrence Sromovsky, University of Wisconsin-Madison/W.W. Keck Observatory

Uranus and Neptune are a distinct class of planets in the solar system. The gas giants Jupiter and Saturn are primarily composed of hydrogen and helium. The ice giants Uranus and Neptune, by contrast, are believed to have formed further from the sun where ices would have been more common. As a result, these are water worlds (although the water is under tremendous pressure and believed to be in an ionic state and mixed with ammonia and methane). Above the water are atmospheres of hydrogen and helium and below rocky cores. However, the report notes that with our current knowledge, Uranus and Neptune, “challenge our understanding of planetary formation, evolution and physics.” We also have learned that planets of their size are a common class of worlds orbiting other stars.

We need to return to these worlds to both understand our own and other planetary systems.

In one way, exploring the solar system is like building medieval cathedrals. It is a process that takes generations. If the plans laid out in the report come to fruition, almost six decades will pass between the Voyager 2 flybys of these worlds and their next visit. Approximately a quarter century will pass from today to arrival. This is not unusual. Nearly a quarter century will also pass between the first serious discussions I’m aware of for a dedicated mission to Europa and the expected arrival of the Europa Clipper spacecraft. Now is the time to begin serious planning to take advantage of the good flight opportunities around 2030.

The goal of the report is to provide the planetary community a range of options it can use when they consider goals for planetary exploration in the 2020’s and early 2030’s. That process, called the Decadal Survey, looks across the solar system and recommends a balance of missions to address top scientific questions within the expected budget. The last Survey, covering 2013 to 2022, ranked a mission to Uranus as the third priority after a rover to cache Martian samples and a mission to explore the habitability of Europa. Available funding allowed development of those latter two missions to begin this decade. The possible start of work on a mission to Uranus was deferred to the 2020s. With that delay, the changing alignment of the planets opens up the alternative to explore Neptune instead of Uranus.

The first use of the report will be by a committee conducting a mid-term assessment of the current Decadal Survey. According to Dwayne Day, the study director of the National Academies' mid-term assessment, the review committee has already been briefed about the ice giants study and has also heard from the Outer Planets Assessment Group about future outer planets missions. Dr. Day was involved in running previous the planetary Decadal. He notes that one of the challenges that group faced was that few planetary mission studies had been done prior to the last Decadal Survey, which limited the options the survey members had when they started. That created a crush during the study to develop new mission concepts and conduct mission evaluations while the survey was underway. Having the ice giants study in hand prior to the development of the next Decadal Survey is a real asset.

The report is a menu of options: perform a flyby only (not recommended), orbit Uranus or Neptune or both (each have unique characteristics), possibly deliver a probe that would enter the atmosphere (recommended), and carry 3, 7, or 13 (recommended) orbiter instruments. There’s also a choice of launch vehicles.

With all these options, it can be difficult to answer what was my basic question in reading the report: When we return, how will we explore whichever world is prioritized in the next Decadal Survey? In this post, I take one set of options and look at that question. For anyone reading the report, this generally follows Option 5 for a Uranus orbiter but with seven instead of three orbiter instruments listed for this option. I also look at how the goals would change if Neptune were selected instead.

I recommend Jason Davis' post on the Planetary Society's blog for additional background on the scientific reasons for returning to these worlds.

Summary of several of the mission options examined by the ice giants study team. Click on the image for a larger view. Credit: Ice Giants Pre-Decadal Study Final Report.

Transit, Arrival, and Orbit

For the most part, the cruise to Uranus would have the spacecraft in quiet mode with periodic status checks with home. Venus and Earth encounters en route could provide opportunities to check out the instruments and observation modes. Many of the trajectories include a flyby of Jupiter that could present opportunities for new science. The spacecraft would carry a new class of instrument, a Doppler imager (more on this later), that could extend our knowledge of the planet’s interior following the Juno mission. (The report doesn’t discuss opportunities for Jupiter science, but given the extensive observations by the Cassini and New Horizons spacecraft as they flew by Jupiter, an ice giant mission is likely to do so, too.)

Long range observations of Uranus would begin 85 days before arrival, and an atmospheric probe would be released 25 days after that. The hours around arrival would be crowded with relay of the data from the atmospheric probe, the orbital insertion burn, and a pass so close to the planet that the spacecraft skims the tenuous upper fringe of the atmosphere.

Once in orbit, the spacecraft would spend two plus years studying the Uranus system. Each standard science orbit would take approximately 50 days. During distant portions of the orbits (greater than 20 Uranus radii), the narrow angle camera would observe the entire planet and the ring system. Closer in, the spacecraft divides its time between high resolution observations of the clouds, rings, moons and the magnetosphere. The example tour presented in the report would include two close flybys of the moon Titania and three each for Oberon, Umbrial, Miranda, and Ariel. The report notes that at the end of the mission, the orbiter might perform a series of orbits that has it, as the Cassini spacecraft is doing at the end of its Saturn mission, fly between the inner ring and the top of the atmosphere. If done, these orbits would allow close up gravity and magnetic field measurements.

Example orbital tour at Uranus that would provide multiple flybys of the major moons and close examination of the rings and atmsophere. Credit: Ice Giants Pre-Decadal Study Final Report.

Science

The report lists twelve science goals. Depending on the instrument compliment, the full range of the Uranus system could be explored: the interior of the planet, the dynamics of the atmosphere, the many minor and five large moons, the ring system, and the magnetosphere. To keep this post to a readable length, I’ll focus on just the top two – determine Uranus’ composition and interior structure – and the examination of the major moons to determine which if any might be ocean worlds.

We now understand that Jupiter, Saturn, Uranus, and Neptune migrated following their formation to eventually reach their present orbits. Understanding the location and manner of the formation of an ice giant would provide missing puzzle pieces to understanding the history of the earliest outer solar system. The goal is to measure the precise ratios of key elements and isotopes in the atmosphere because they act as fingerprints identifying the actual circumstances of planetary birth and evolution.

Addressing these questions would be the job of the atmospheric probe. During its descent through the upper atmosphere to a depth where atmospheric pressure equals at least ten times the sea level pressure on Earth, its mass spectrometer would measure the composition of the gasses. Additional instruments would measure temperature, pressure, density to provide context (and contribute to understanding the planet’s weather). If space within the probe and budgets permit, this probe could carry additional instruments such as an instrument to detect cloud layers.

Current understanding of the interior structure of the gas and ice giant planets. Credit: Ice Giants Pre-Decadal Study Final Report.

As with the ice giant’s formation, our understanding of their interior structure is poor. The current model has an outer gaseous atmosphere composed primarily of hydrogen and helium, a large inner ocean composed primarily of ionic water, and a rocky core. The existing data from the Voyager 2 flybys, however, is ambiguous. The primary instrument to address this question on a new mission would be one that has never flown on a planetary spacecraft. A Doppler imager would look for oscillations at the top of the atmosphere caused by motions at a range of depths within the atmosphere and ocean. Just as seismic waves in rocky worlds reveal their interior structure, these atmospheric motions would reveal the interior structures of gas and ice giants. The same method is used to study the interior of the sun. The report notes that these measurements hold the promise to revolutionize the study of outer planet interiors over the current methods that use planets’ gravity fields to study interiors. (Measurements during a Jupiter flyby would be as novel as those at Uranus or Neptune.) The measurements, however, are data hungry, requiring images be taken as frequently as every two seconds during the approach to the planet.

Voyager 2 images of the five larger moons of Uranus. Credit: Ice Giants Pre-Decadal Study Final Report.

The five major moons of Uranus fall within the same size range as Saturn’s medium sized moons such as Enceladus, Mimas, and Dione. Voyager 2’s low resolution (except for the inner most of these moons, Miranda) observations revealed that all five show signs of varying degrees of past resurfacing from cryovolcanism and tectonic activity. The two innermost, Miranda and Ariel appear to have extensive resurfacing while the two outermost, Titania and Oberon, are large enough that they may have liquid oceans between their outer icy shells and inner rocky core. Titania has comparatively few large craters, suggesting a younger surface, than the more cratered Oberon. Titania also has a series of surface ridges similar to those on Europa’s surface. The middle of these moons, Umbriel, appears to have the least altered and most battered surface.

During the satellite tour, the orbiter’s camera would image their surfaces to allow scientists to reconstruct their past geologic history. If the craft carries more than just the minimal core instrument complement, imaging spectrometers would be used to measure the surface composition, which likely includes material erupted from the interior. The magnetometer would be used to search for induced magnetic fields at the moons that would strongly suggest a present interior liquid ocean. (This is how the Galileo spacecraft all but confirmed the existence of Europa’s ocean.) Radio tracking of the spacecraft’s signal would be used to measure the sizes of the icy shells, any ocean, and the rocky cores. The wide range of sizes (from Miranda’s 472 kilometer diameter to Titania’s 1577 kilometer diameter) and geologic variety makes the Uranus system a laboratory for understanding how systems of moons formed and evolved and their potential for providing habitats for life.

If Neptune Instead of Uranus

The report describes two options for missions that target Neptune instead of or in combination with Uranus. Because Neptune lies further from the sun, and orbiter and probe mission would require a larger and more expensive launch vehicle than the Uranus mission plus a solar electric propulsion stage to provide an additional velocity boost beyond what the launch vehicle and the gravity assists from Earth and Jupiter can provide. Total flight time to Neptune with this combination would take thirteen years, one more than to Uranus without the solar electric propulsion stage.

Voyager 2 image of Neptune's moon Tritan. Credit: JPL/NASA

For this mission, the science goals for studying the planet, its rings, and minor moons are essentially the same as for Uranus. The key difference is that Neptune possesses one extremely large moon, Triton, that is likely a sister world to Pluto that was captured from the Kuiper belt. Triton has a thin atmosphere, erupting (at least at the time of the Voyager flyby) geysers, and possibly an ocean beneath the ice shell. This moon would be a focus of the orbital mission with 36 encounters. The science goals would be similar to those for the larger Uranus moons with the addition of studying the composition of the atmosphere with an ultraviolet spectrometer as was done by the New Horizon’s craft at Pluto.

The report also briefly discusses the possibility of sending an orbiter to Uranus and a flyby spacecraft to Neptune. For this option one orbiter would conduct the in-depth studies the committee felt were essential while the flyby craft would expand the studies to the second ice giant. One of the two craft would carry an atmospheric probe. In this case, the Neptune flyby would likely be similar to a Uranus flyby considered by not recommended in the report. The Neptune flyby craft would conduct approach science as described for the Uranus orbiter above. The craft would then likely conduct a close flyby of Triton to provide single close up examination of it before heading into the deep outer solar system and possibly into interstellar space.

Getting There

It’s possible to traverse the realm of the ice giants quickly – the New Horizons spacecraft reached even more distant Pluto in just under a decade. However, that spacecraft was intentionally kept as light as possible to allow a high velocity launch. While New Horizon’s was a bantam-weight scout, scientists want a highly capable orbiter for what likely would be a once-in-several-generations mission to orbit one of these worlds. The proposed ice giant orbiters would be approximately 2000 kg without fuel, or about five times the mass of the New Horizon’s spacecraft but about the same as the Cassini Saturn orbiter.

Even if the launch vehicle existed to directly fling the heavier ice giant orbiter to its destination, a New Horizon style mad dash wouldn’t be possible. When it reached Pluto, that spacecraft was going so fast that it would have been impractical to carry enough fuel to insert itself into orbit. The mission design for an ice giant mission becomes a trade off between speed and the mass of the fuel needed to brake from that velocity into orbit. Using the a mid-range commercial launch vehicle such as the Atlas V, a reasonable balance results in the twelve-year flight listed above.

Using a more expensive Delta IV Heavy, a year to a year and half can be cut from the transit time. If an SLS booster is available with its greater launch ability, the flight time can be cut by four years. Adding a solar electric propulsion unit to provide a boost in flight could cut the flight time a year. Any combination of these latter options comes with the trade off of a higher, and possibly much higher, overall mission cost. (When it becomes available, the Falcon Heavy will provide an additional option.)

Example trajectory for a mission to orbit Uranus (Option 5 from the report). Credit: Ice Giants Pre-Decadal Study Final Report.

Another challenge for exploring these worlds is that the sun is too faint for solar power so radioisotope power supplies would be required. Over time, the components of these supplies degrade, reducing power to the spacecraft. (The radioisotopes also decay, but that loss is slower.) An enabling technology for these missions is an enhancement already under development that boosts power delivery late in a mission’s life by incorporating longer-lived components. (For those of you who follow these technologies, this is the enhanced Multi-Mission Radioisotope Thermal Generator, or eMMRTG). The proposed designs would carry either four or five eMMRTGs. (The Curiosity rover, by comparison, carries just one of the current generation MMRTGs.) At the projected end of these missions, the combined output from the multiple eMMRTGs will be less than either four or five 100 Watt light bulbs, depending on the number carried.

Conceptual design for a Uranus orbiter and atmospheric probe. Credit: Ice Giants Pre-Decadal Study Final Report.

The report notes that the expected power will require turning instruments on and off because not all can operate at the same time. That act stresses the electrical components such as solder joints. Instruments for missions to Uranus or Neptune may, the report notes, may require additional levels of redundancy be built in to ensure they can operate for the full length of the missions.

Another challenge imposed by distance is returning the data collected. At Uranus, the data rate would be approximately 0.37 to 0.52 gigabits per day, or approximately one-fifth to one-seventh the rate planned for the Europa Clipper mission which will operate at the much closer Jovian system. The report notes that arbitration for the available data bandwidth between the different scientific investigations will be “complex.”

The Next Steps

As discussed in the introduction to this post, planning missions for the outer solar system is a long game. A key decision will come in the rankings of priorities of missions in the next Decadal Survey. Then, assuming a high ranking, the size of NASA’s planetary science budget will determine its capabilities, and whether just one or two of these worlds will be explored. A mission to either of these worlds would have similar costs – ranging from around $2 billion to $2.3 billion depending on options – to other large planetary missions such as NASA’s Curiosity rover.

The estimated relative science benefit (vertical axis) versus estimated cost of different mission options using the minimum three instrument payload recommended for the flyby or orbiter spacecraft. The study team concluded that the limited science from a flyby mission would not be worth the cost savings from the much more capable orbiter mission. Sending missions to both planets was judged to approximately double the science return but at substantially higher costs. Credit: Ice Giants Pre-Decadal Study Final Report.

While the report focuses on a US-only mission, the study was done with the hope that exploring these worlds could be done as an international project. Scientists in Europe have proposed their own missions. The report recommends a further study to explore the options for collaborative missions to these worlds. Working together, a mission becomes more affordable to both agencies and the chances for a more capable mission, or even missions to both worlds, seems more likely. Other space agencies might also be interested. The case for exploring these worlds is compelling, and I am optimistic that we will.

A Great Proposed Budget for Planetary Science

2017-05-23T23:27:00.000-07:00

The Trump administration has released its first full budget proposal for the federal government, including NASA. While many science programs throughout many agencies face recommended cuts (see these analyses by the journals Science and Nature), NASA’s science programs generally fared well. The Planetary Science program fares particularly well. Several satellite missions and research programs in the Earth Sciences program that focus on climate change and carbon monitoring, by contrast, face termination. NASA’s Astrophysics (including the James Webb Space Telescope) and Heliophysics programs are projected to have flat budgets into the future.

Past and proposed spending for NASA science programs. The Planetary Science program is the only program proposed to receive a major increase.

For fans of planetary exploration, I think it’s time to pop the champagne. The proposed budget takes the NASA program to new spending heights. While much of the proposed Trump budget seems likely to get mauled by Congress, the latter’s strong support for the planetary program implies that this program’s proposed increase may become reality.

The budget documents provide two sets of numbers. The first, and most important, are specific requested amounts for Congress to approve for the Fiscal Year 2018, which starts October 1, 2017. The second set of numbers are projected notional budgets for FY19 to FY22. This provide guidance for future years and is important because NASA’s managers cannot plan programs that aren’t projected to be funded in the out years.

Past and proposed budgets for the planetary science programs that develop and operate missions. It is normal for budget lines to wax and wane as the development of individual missions ramp up their spending leading to launch followed by a ramp down as another program's missions approaches peak funding. In the planning period, Mars program funding ramps down as the 2020 rover development completes followed by an increase to support a follow on mission. The Discovery program ramps up to support development of the Lucy and Psyche missions with the start of a second ramp for a follow on mission. The New Frontiers program ramps down following the launch of the OSIRIS-REx mission followed by a ramp up for a new mission. The Outer Planets and Ocean Worlds program, which is dominated by spending to develop the Europa Clipper mission is project to have erratic swings not explained in the budget documents.

Here are some of the highlights of the proposed Planetary Science budget:

Every single mission in flight that is expected to still be operating next year (rest in peace Cassini and Dawn) is funded for the next year. Four missions are projected to remain funded for a further five years: the Lunar Reconnaissance Orbiter, the Mars Reconnaissance Orbiter, the OSIRIS-REx asteroid sample return spacecraft, and the Curiosity rover. The Juno mission is projected to be funded through 2020, which would allow the mission to complete most of its originally planned orbits. The New Horizon mission is funded through its encounter with the small Kuiper Belt object, 2014 MU69 in 2019. However, the Opportunity rover is forecasted to be funded only through 2018 and the Mars Odyssey Orbiter through 2019. The budget documents don’t give an explanation for the limited funding for these two missions; perhaps this is an expectation that these aged craft will not live forever.

All mission currently in development are funded including the Mars 2020 rover, the Europa Clipper mission, and three Discovery missions: the InSight Mars geophysics station and the Lucy and Psyche asteroid missions. Funding is projected to develop the next New Frontiers mission to be selected in late 2018 or 2019 and launched in the mid-2020s.

The projected budget shows funding for NASA to select and begin development of the next Discovery mission after the Lucy and Psyche missions are launched. Given the timing of the selection in the early 2020s, launch would likely be in the mid-2020s. The budget request also forecast the start of development of a Mars mission that seems likely to launch in the mid-2020s. While the budget document is silent on the nature of this mission, NASA has said that it would like to fly a new orbiter to replace the venerable Mars Reconnaissance Orbiter.

If you want to look for disappointing news in the proposed planetary budget, I found two. The document projects a funding ramp for the Europa Clipper mission that would enable a launch in the mid- to late-2020s. This is in direct conflict with Congress’ stated goal that the mission should launch by 2022. The requested funding for FY18 would support the 2022 launch. The key will be whether funding on follow on years is greater than that projected in the budget document. For example, the projected spending in FY19 is $303 million versus $580 million needed to launch in 2022.

The other potentially disappointing news is that the budget request explicitly rules out starting development of the congressionally mandated Europa lander, which would follow the Europa Clipper mission.

To meet Congress’ stated goals for the Europa Clipper and lander missions, the planetary science budget would need to grow substantially starting in fiscal year 2019, or other missions within this budget would have to be cut.

A look at the larger federal budget situation does suggest a problem with the rosy picture for planetary exploration in this budget. There are at least three camps in Washington DC with vastly different views on what the federal budget should look like: the Trump administration, Congressional Republicans (who may have fractured views of their own), and Congressional Democrats. The overall Trump federal budget proposes radical changes to spending for many agencies (NASA among the few excluded). It seems likely that resolving these differences may extend well into 2018 or perhaps never. (Resolving much smaller differences for the FY17 budget occurred eight months after the start of the fiscal year.) The standard way to deal with impasses is to pass a continuing resolution that extends the previous year’s funding into the next for a period of time (and sometimes the entire year). Several missions in development – the Mars 2020 rover, Europa Clipper, and Lucy asteroid mission – require large increases in their budgets next year to stay on track. Long-lasting continuing resolutions could cause these missions to miss their launch dates, raising the overall costs of the missions.

The budget document did have one surprising piece of potential news. The Psyche asteroid orbiter mission has been slated to launch in 2023 and arrive at its metallic namesake in 2030. The mission’s websites state these dates. However, the budget document states that the mission will launch in 2022 and arrive at its destination in 2025. A typo or more aggressive funding allowing an earlier launch and arrival?

Explorer of Enceladus and Titan

2017-01-29T15:17:00.001-08:00

The search for another world with life in our solar system has arguably become the most powerful theme in planetary exploration. While microbial life – the most likely form of life elsewhere in the solar system – itself is likely to be hard to prove with a unified series of past, current, and planned missions to Mars. NASA is developing an orbiter to investigate the habitability of Europa and studying a follow on lander to directly search for life. And for the third time in less than a decade, scientists have proposed a multiple-flyby mission to explore the habitability of Saturn’s ocean moons Titan and Enceladus.

The latest proposal, led by European scientists, is called Explorer of Enceladus and Titan (E²T). It builds on the experience gained from two less ambitious previous proposals, led by American scientists, the Journey to Enceladus (JET) in 2010 and the Enceladus Life Finder (ELF) in 2014.

I met the principle investigator for the E²T proposal, Giuseppe Mitri with the University of Nantes, at a conference in December. We discussed his team’s proposal and he has subsequently provided me we a comprehensive look at the goals and the mission implementation. In an email to me, he explained the motivation for the mission: “Enceladus and Titan are two unique worlds in the Solar System not only in terms of their geology and evolution but also for their habitability. Flyby missions such as E2T provide an unprecedented opportunity to explore in detail, surpassing that of Cassini, two worlds in a single relatively low cost mission”

Credit: Guiseppe Mitri and the Explorer of Enceladus and Titan team

For scientists interested in habitability and life, Titan and Enceladus are obvious targets for exploration. The Cassini spacecraft, which is nearing the end of its thirteen year exploration of the Saturn system, discovered that both worlds have salty water oceans beneath icy crusts. Titan also has a rich stew of organic molecules in its atmosphere that are deposited on its surface and into its methane-ethane surface seas. Enceladus conveniently has plumes jetting samples of its ocean into space. Within the plumes, Cassini’s instruments have found organic molecules and trace minerals suggestive of hydrothermal water-rock interactions that could provide a habitat for microbes.

The three proposed missions to Enceladus and Titan would employ relatively simple spacecraft with just two to three instruments. They stand in contrast to NASA’s planned mission to explore the habitability of Europa, another ocean world. The Europa mission will bristle with nine instruments, several of which will produce floods of data that require a high-powered communications system to return the data to Earth.

A key difference between the Europa and the Saturn moons missions is the prior history of exploration. Europa was explored by the Galileo spacecraft built with 1970s technology that had a crippled communications system. As a result, NASA’s new Europa mission must conduct its own comprehensive global study of this world. At Saturn, this initial investigation of Enceladus and Titan has been conducted by the highly capable Cassini spacecraft built with 1990s technology. As a result, the next mission to these moons can focus on a few specific questions answerable with two to three instruments.

(For those of you who recall that the Galileo spacecraft explored Jupiter’s system in the 1990s, the completed spacecraft sat on the ground for almost a decade due to launch delays.)

Two of the E²T spacecraft’s instrument would focus on in situ composition measurements. At Enceladus, the spacecraft can fly through the plumes and directly taste the ocean’s contents. At Titan, complex organic molecules are carried to the outermost fringes of the atmosphere where the spacecraft can sample the atmosphere’s chemistry.

The E²T spacecraft’s two mass spectrometers would sample material during each passage and determine their composition by “weighing” their constituent molecules. The distribution of the weights of the different molecules can be interpreted to determine the composition of the original material. The spacecraft’s ion and neutral gas mass spectrometer would determine the composition of gasses while the Enceladus Icy Jet Analyzer would determine the composition of ice, salt, and dust particles in Enceladus’ plumes. The two mass spectrometers will measure the nature of the organic chemicals, the pattern of carbon isotopes, the relative abundances of noble gases, and search for amino acids and abnormal isotope rations in organic molecules that suggest a biological origin.

The Cassini spacecraft carried versions of both these instruments, but the E²T instruments would have a forty to fifty times improvement in resolution (the ability to distinguish similar molecules) and sensitivity (the ability to measure minute amounts of a substance) over their predecessors. (NASA’s Europa mission would carry similar instruments to E²T’s as will Europe’s JUICE mission to Jupiter and its moon Ganymede).

The E²T team has several key questions that the two mass spectrometers would address. For Enceladus, are the materials in the plume most likely from its formation or from current geological or biological processes? What does the composition reveal about the nature of the liquid reservoir (currently believed to be a global ocean beneath an icy cap) and its potential as a habitat for life? For Titan, what are the sources of its volatiles and how they have been subsequently processed? Does the atmospheric composition suggest that the current atmosphere is refreshed by material reaching the surface from the deep water ocean?

The E²T’s spacecraft’s third instrument would image Titan’s surface and the sources of Enceladus’ plumes (the so called ‘tiger stripes’) in the near- and short-wave infrared. (The instrument’s name spells out TIGER for the Titan Imaging and Geology, Enceladus Reconnaissance camera.) Titan is perpetually shrouded in atmospheric haze, hiding the surface from cameras that image in most wavelengths. However, spectral windows at 1.3, 2, and 5 microns allow a camera to image the surface at several times finer resolution than a similar instrument on the Cassini spacecraft (and also at better resolution than Cassini’s radar images). The images returned by the camera will address several key questions such as: To what degree are sediments produced and transported by fluvial and aeolian processes? How have the rivers and seas of liquid methane and ethane modified the surface? How does the composition of the surface, revealed by the three ‘colors’ of the spectral bands, vary?

If the E²T mission is selected as a finalist in ESA’s medium class competition, the team will investigate whether a radio science experiment to study the two moons’ gravitational field could be added. If it is, this experiment will investigate the thickness and mechanical properties of the ice shell at Enceladus’ southern pole where the plumes originate. The gravity measurements would also be used to investigate Titan’s ice shell and the properties of its internal ocean.

The E²T team hasn't release a description of its planned imaging coverage of Titan's surface or flights through the plumes of Enceladus. However, the similar JET proposal would have imaged large portions of Titan's surface at several times the resolution of Cassini's instruments and flown through the plumes at different altitudes. Credit: JPL/Caltech

	JET	ELF	E²T
Neutral and ion mass spectrometer	X	X	X
Particulate mass spectrometer		X	X
Infrared camera	X		X

Comparison of instruments proposed for the three proposed Saturn orbiters that would perform multiple flybys of Enceladus and Titan. The E²T team is proposing a more ambitious mission than did the preceding teams.

If Titan and Enceladus are obvious targets for further exploration, what is surprising about E²T and its predecessor proposals is that they were put forward for the lowest-cost class of missions flown by the European Space Agency (ESA) and NASA to explore the planets.

Both ESA and NASA have mission categories for similarly priced low cost planetary exploration. For the Europeans, this is the Medium class mission program where missions can be proposed for planetary science, astrophysics, or heliophysics. For the Americans, this is the Discovery program that is dedicated to the exploration of the solar system. These programs cap the cost for costs directly managed by the mission’s principle investigator at €550 million for ESA and $450M for NASA. (A Euro spent in Europe and a dollar spent in the United States have similar purchasing power.) For the ESA missions, the cap must cover the spacecraft, mission operations, and launch but doesn’t include the costs of instruments, science teams, or data analysis, which are paid for separately by individual nations. For NASA missions, the cap must cover the spacecraft, instruments and the science team (except those contributed by foreign nations) but doesn’t include launch or mission operations, which are paid for separately by NASA. (The difference in the way instrument costs are accounted for by ESA and NASA explains why European mission proposals typically include more instruments than similar American proposals. For European missions, instruments are off the PI’s budget. US proposers like to include foreign instruments paid for by their governments because they again are off the PI budget.)

Once all costs are added up, these missions typically cost somewhere in the neighborhood of 600 to 700 million Euros or dollars. However, this is still only about 60% of the cost of the cheapest outer planets mission to date, the Juno Jupiter orbiter, at $1.1 billion. (The Juno spacecraft has to survive Jupiter’s intense radiation levels, which are absent at Saturn, accounting for a portion of its greater costs.)

Developing a winning proposal for a mission to Saturn for less than €700 million is challenging. Per the abstract for an upcoming conference, the JET and ELF missions “were rejected [by NASA] for too-high cost risk.”

The E²T proposal, however, incorporates the lessons learned from those earlier proposals, and scientists from the earlier efforts are members of the E²T team. We aren’t privy to all the details of how the E²T team proposes to fit within the budget cap. This information is a key part of the proposal’s competitive edge. (The presentation on the mission supplied to me by Dr. Mitri, for example, has a number of figures removed because they would reveal too much about key details of the proposal.) However, the team has shared enough information about the mission to reveal some of the key strategies.

As described above, the E²T would have limited, focused science goals allowing for a simple, low-cost spacecraft. Once at Saturn, the spacecraft would orbit Saturn with six flybys of Enceladus and seventeen flybys of Titan over 3.5 years. In the weeks between encounters, the spacecraft would leisurely return each flyby’s data to Earth. This enables a lower peak data return rate, which ripples through the spacecraft’s design, lowering mission costs. Having just three instruments and substantial time between encounters also reduces the number of mission controllers needed, again reducing costs.

The E²T team hasn't release a description of its planned orbits around Saturn to explore Enceladus and Titan. However, the similar JET proposal would have used orbits to encounter Titan in multiple locations to allow imaging of different hemispheres. A series of orbits would have provided flights through Enceladus' plumes. Credit: JPL/Caltech

The E²T team proposes to use a shared launch to a geostationary transfer orbit with another spacecraft such as a communications satellite. Splitting the launch cost would save the E²T up to 60 million Euros, or enough to pay for much of the cost of mission operations on the way to Saturn. This strategy is enabled by using solar electric propulsion, which allows the spacecraft to propel itself out of Earth orbit and reach Saturn in just six years. (The JET mission would have required 7 to 8.5 years and ELF ~10 years to reach the ringed world.) Once at Saturn, the spacecraft would use chemical propulsion to enter orbit and set up its encounters.

Further cost savings would come from using solar power to generate electrical power instead of the more costly plutonium-powered radioisotope generators. (Although part of the reason for this choice is that ESA lacks the technology for radioisotope generators and US law prohibits NASA from supplying one for a foreign spacecraft.) By using massive solar arrays of 160 square meters (compared to around 70 square meters for the Juno spacecraft), the spacecraft can create a comfortable 620 Watts of power at Saturn. While a portion of this power will need to go to heaters to keep the spacecraft and its instruments warm (around half of Juno’s power is reserved for this), the E²T mission would have ample power margins.

The E²T spacecraft would use massive solar arrays to gather enough sunlight at Saturn to produce electrical power. Credit: Guiseppe Mitri and the Explorer of Enceladus and Titan team

It is these large solar arrays that enable the spacecraft to return the data from mapping Titan’s surface. The ELF mission, by comparison, would have had smaller solar arrays and would have lacked the power to return imaging data. (The JET mission would have used radioisotope generators, which would have supplied enough power, and spare heat, to enable the mapping of Titan.)

The E²T proposal also has another advantage over its predecessors. If the mission is selected by ESA, the team would have almost five years to refine the design before the actual implementation begins. This is more time to fine tune cost savings and to take advantage of advances in spacecraft technology that have the potential to reduce costs. NASA’s Discovery missions, by contrast, have to be ready to begin implementation immediately after their selection. As a result, the proposing teams must have resolved all key design issues at the time of the proposal.

The most encouraging sign for me, though, about the E²T concept is that the community of scientists interested in exploring Titan and Enceladus continue to put forth similar if more refined proposals. Preparing for these mission competitions is time consuming and expensive. If the budget math wasn’t close, I don’t believe they would keep coming back. Another fact to consider is that in NASA’s Discovery program, teams often propose missions several times, incorporating the lessons learned each time their proposals are passed over. The E²T team builds on the experience of two previous proposals.

If the E²T proposal is passed over, the Discovery program may hold another lesson. The team behind the OSIRIS-REx mission on its way to do a sample return from the asteroid Bennu twice unsuccessfully proposed their ideas to the Discovery program. Their efforts finally succeeded when they proposed to NASA’s New Frontiers program, which at the time allowed PI costs of around $800M. NASA has begun the competition for its fourth New Frontiers mission, and proposals for missions to Titan and Enceladus are requested (along with proposals for missions to five other solar system destinations). I expect that at least one mission similar to E²T, perhaps with more instruments, will be proposed. (We may also see teams used the additional funding available to propose a sample return from Enceladus’ plumes or a Titan lander. At the time of the JET proposal, a Titan lake lander also was proposed for the Discovery program but not selected.)

ESA will announce the list of finalists for its competition this June, NASA will announce its list in November. If selected, an ESA mission to Titan and Enceladus would launch around 2030 while a NASA mission would launch around 2025. These two competitions likely represent the best hope for fans of these two worlds to see a spacecraft arrive at Saturn by the mid-2030s.

Lucy and Psyche Asteroid Missions

2017-01-06T16:59:00.001-08:00

Earlier this week, Santa in the guise of NASA managers brought the solar system small bodies science community a sack full of belated Christmas presents. The Venus science community was unfortunately left with no presents under the tree.

As I’m sure almost all of the readers of this blog are aware, the space agency announced that it selected the Lucy multiple asteroid flyby mission and the Psyche asteroid orbital mission as its thirteenth and fourteenth missions in its low cost Discovery program. In addition, the NEOCam space telescope mission to discover and map large numbers of asteroids was awarded an additional year’s funding for its team to mature its design.

An artist’s conception of the Lucy spacecraft flying by the Trojan Eurybates and the Psyche spacecraft in orbit around asteroid 16 Psyche. Credit: SwRI and SSL/Peter Rubin

The losers were a Venus mapping mission and Venus atmospheric probe mission. Their rejection will continue a drought in NASA launches to our sister world that followed the Magellan mission’s launch in 1989. When asked why neither Venus mission was selected, the head of NASA Planetary Science division, Jim Green, answered that the competition for selection was among mission proposals and not between destinations. He said that the review teams found that the proposals for the Venus missions scored less well than the proposals for the selected missions.

Dates for key events in the Lucy and Psyche missions.

Lucy Mission	Encounter date	Location	Dia-meter (km)	Spectral type
Launch	Oct. 2021
DonaldJohanson	April 2025	Main belt	3.9	C
Eurybates	Aug. 2027	Greeks	64	C
Polymele	Sept. 2027	Greeks	21	P
Leucus	April 2028	Greeks	34	D
Orus	Nov. 2028	Greeks	51	D
Patroclus/Menoetius	March 2033	Trojans	113/ 104	P
Psyche Mission
Launch	Oct. 2023
16 Psyche	2030	Main belt	210	M

The Lucy mission, named after the famous humanoid fossil, will survey two asteroid fossil beds for clues to the early history of the solar system. It will study the Trojan asteroids that share Jupiter’s orbit, either preceding (the “Greek” camp in L4 Lagrangian orbits) or trailing (the “Trojan” camp in L5 Lagrangian orbits) the giant planet. Telescope observations suggest these bodies have primitive compositions, several of which don’t appear to be represented in our meteorite collections and that haven’t yet been visited by spacecraft.

The planned orbits and asteroid encounters for the Lucy mission. Credit: SwRI

The origin of these asteroid populations is a mystery, and its solution would tell scientists much about the dynamics of the young solar system. Planetary scientists now believe that the orbits of the giant planets migrated in toward the sun and then out again soon after their formation. In the process, they scattered asteroids and comets hither and thither. Jupiter’s Lagrangian orbits may have been sticky gravitational traps that caught a diverse sample of bodies that originated from throughout the outer solar system to its fringes. Another theory suggests that the Trojans originated in the same region as Jupiter and followed it in its movements and are therefore samples of conditions where Jupiter formed. Either way – and it’s possible that the present population represents a mixture of sources – these bodies hold clues to conditions and processes from the infancy of our solar system.

The most recent planetary decadal survey emphasized the importance of these bodies by prioritizing a mission to explore them. “Trojan asteroids, at the boundary between the inner and outer solar system, are one of the keys to understanding solar system formation. Originally thought to have been captured from the outer parts of the asteroid belt, Trojan asteroids are proposed in new theories to have been captured instead from the Kuiper belt during a phase of extreme mixing of the small bodies of the solar system. In-depth study of these objects will provide the opportunity to understand the degree of mixing in the solar system and to determine the composition and physical characteristics of bodies that are among the most primitive in the solar system.”

The report listed three key questions related to the study of Trojan asteroids in context with other bodies throughout the outer solar system:

What were the initial stages, conditions, and processes of solar system formation and the nature of the interstellar matter that was incorporated? Important objects for study: comets, asteroids, Trojans, and Kuiper belt objects.
“What governed the accretion, supply of water, chemistry, and internal differentiation of the inner planets and the evolution of their atmospheres, and what roles did bombardment by large projectiles play? Important objects for study: Mars, the Moon, Trojans, Venus, asteroids, and comets.
“What were the primordial sources of organic matter, and where does organic synthesis continue today? Important objects for study: comets, asteroids, Trojans, Kuiper belt objects, Enceladus, Europa, Mars, Titan, and Uranian satellites.”

The Lucy looks to the New Horizon Pluto mission for two of its instruments with near copies of that mission’s LORRI high resolution camera and the RALPH color camera and imaging spectrometer. The third instrument is a thermal emission spectrometer derived from an instrument on the OSIRIX-REx asteroid mission. Data from these instruments will provide information on the processes that shaped these worlds, their composition, and physical properties of the surface material such as the average size of particles. Tracking of the spacecraft’s radio signal will provide information on each asteroids mass and therefore density which provides clues to their composition and to whether they are solid objects or rubble piles.

The creativity behind the Lucy mission is that its proposers found a trajectory that over 12 years encounters seven asteroids (two in a binary system). The Lucy mission will encounter its targets using two large solar orbits that take it out to the orbit of Jupiter to encounter the Trojan swarms. In the first of these orbits, it will fly by a tiny main belt asteroid (DonaldJohanson, named after the paleontologist who led the team that found the Lucy fossil) and then four diverse asteroids in the Greek population. The next orbit takes it into the Trojan population for a single encounter with a binary asteroid system whose characteristics are similar to those of comets suggesting they may be refugees from the distant outer solar system. After this second long orbit, the spacecraft should have sufficient fuel for further encounters with main belt and Trojan asteroids in a third orbit if NASA approves funding for an extended mission. (Each of these extended orbits appear to take approximately six years, so any encounters from an extended mission seem likely to occur in the late 2030s.)

The Lucy mission will study a variety of asteroids through brief, but intense flybys. It will be something like photographing boulders along the roadside while speeding by on a freeway for later analysis. The second Discovery mission selected, by comparison, will be like parking your car next to one especially intriguing boulder for a nearly yearlong examination.

The single destination for the Psyche spacecraft will be the relatively large asteroid of the same name. This world is the largest of the rare (type M) metallic asteroids. Psyche could be unique remnant of a class of asteroids that formed so close to the sun that only metals could condense out of the early solar nebula and was later flung into the main belt of the asteroids. Or it could be the inner, metallic core of a once larger protoplanet that had its overlying layers of rock and possibly ice blasted off by impacts with other asteroids.

Telescopic observations reveal that Psyche’s surface is 90% metallic and 10% silicate rock. The spacecraft’s instruments should distinguish between these scenarios by measuring the composition in detail and looking at the arrangement of the silicate material. The mission’s principal investigator wrote me, “If the silicate material is primarily high-magnesian pyroxene or olivine, then these silicates are likely the remnants of a crystallizing magma ocean, and indicate that Psyche started as a differentiated planetesimal and had its mantle stripped, validating the mission’s prime hypothesis for this body. If the silicates are all primitive chondritic material, then they were likely added as later impacts, and Psyche may have started life as a highly reduced metallic body without a significant silicate mantle, or, the nature of impact flux and its consequences are far more significant than our current models indicate. The numbers and shapes of craters on Psyche’s surface may help decipher that story.” The spacecraft’s gamma-ray and neutron spectrometer (derived from an instrument on the MESSENGER Mercury orbiter) will help determine the asteroid’s bulk elemental composition.

Psyche the asteroid won’t be an unchanged relic. Its original surface will have been battered by numerous impacts over the subsequent billions of years. The hydrated materials recently discovered on its surface with telescopic studies, for example, are likely to have been delivered by impacts of other asteroids. It’s possible that by now, the body is a jumbled rubble pile. The cameras on the spacecraft (near copies of the cameras that the Mars 2020 rover will carry) will be tasked with taking the images that will allow geologists to reconstruct its history. By using filters tuned to specific wavelengths of visible and near-infrared light, the camera’s images also will help map the surface’s fine-scale composition.

The planned orbits for the Psyche spacecraft around its namesake. Credit: Psyche mission team.

The Psyche asteroid’s sits deep within the asteroid belt at 3.3 times the Earth’s distance from the sun. (By comparison Vesta is at 2.6, the asteroid Ceres is at 3, and the Trojan asteroids average 5.5 times the Earth’s distance from the sun.) To reach this world, the Psyche spacecraft, like the Dawn spacecraft that has explored Vesta and Ceres, will use solar electric propulsion to slowly but methodically reach its namesake world. The gentle thrust of its engines will deliver the spacecraft to Psyche approximately seven years after launch and will allow it to spiral down to progressively lower orbits. The mission’s planners expect the spacecraft to orbit as close as 105 kilometers from the surface where the cameras will have a resolution of 5 meters.

While not yet selected as an approved mission, the NEOCam telescope was awarded an additional year’s funding to mature its design. For the team proposing this mission, this is the third time it has vied for selection. It was originally proposed in 2006 and not selected as a finalist and reproposed in 2010 when it was awarded funding to mature the technology of its sensors. If the mission eventually is funded by NASA, it would have two goals. The first would be oriented toward protecting our planet by discovering a large number of the small (from a few tens of meters across up to a kilometer), near Earth asteroids that have evaded detection by other means. The second goal would be more scientifically oriented with the NEOCam telescope expected to also observe more than a million main belt asteroids and about a thousand new comets. The resulting database would allow sophisticated analyses on the sizes, compositions, and orbital dynamics of the population of small worlds.

So far as I can recall, this is the first time that a Discovery mission finalist has been awarded additional funds to mature its design to be ready for a future funding opportunity. (Two other missions from the 2010 competition were also given funding to mature instrument technologies, but neither were finalists.) NEOCam’s (this is an acronym for Near Earth Object Camera) focus on small bodies whose orbits lie close to and often cross that of Earth’s places it at the junction of several of NASA’s programs. From finding and mapping the location of these objects, there is good science, there is planetary protection, and there is finding potential worlds for future human exploration or mining. As a result, says NASA’s Green, the additional funding awarded to mature NEOCam’s design is seen as a strategic investment.

Unfortunately, missions to Venus are not seen as a strategic investment and both finalists for this planet are simply left as unselected. I was very disappointed to see that neither was selected. (I had hoped for the selection of one Venus and one asteroid mission.) I believe that this world can tell us much about the evolution of terrestrial planets in our solar system and represents what is likely to be a relatively common class of larger rocky worlds around other stars.

So for fans of Venus and for all the other solar system destinations, what are the opportunities for selection of future missions? The European Space Agency is currently reviewing proposals for its fifth medium class science mission, which would enable planetary missions roughly the same capability as NASA’s Discovery program. I know that there is a proposal for a Venus mapping mission and a Saturn orbiter to study the moons Titan and Enceladus. Based on proposals for the last competition, there are likely to be other missions proposed to study other solar system bodies including orbiting main belt asteroids. The planetary mission proposals are in competition not only with each other but also with astrophysics and heliophysics missions. The selection of finalists for this competition is expected by June, the selection of the final winner is expected around 2019 with a launch around 2029.

NASA has just begun the process to select its next New Frontiers mission, which will have a total budget (likely $1.2 billion or more) 80-100% larger than the Discovery missions (likely $675 million or more). These missions are selected from a pre-approved list of high priority missions. For this competition, this list is:

Comet Surface Sample Return

Lunar South Pole-Aitken Basin Sample Return

Titan and/or Enceladus

Saturn Atmospheric Probe

Venus atmospheric probe and lander

Trojan Asteroid Tour and Rendezvous

We don’t know what the selection of the Discovery Lucy mission, which will study Trojan asteroids, will have on the chances for the selection of a New Frontiers Trojan mission. The selection of the finalist proposals is expected in November, the final selection in mid-2019, and launch by the end of 2025.

Finally, NASA plans – subject to the generosity of the President and Congress with future funding – to launch Discovery missions approximately every three years. With the launch for the Psyche mission in 2023, the 15^th mission in this series should launch around 2026. Working backwards from that date, we might see the start of the next completion late this decade and selection of the next mission(s) in the early 2020s. There were many exciting missions proposed for this just completed competition; many are likely to be re-proposed. And we are likely to see new ideas put forth.

As the selection of Lucy and Psyche shows, these competitions among scientists result in creative and scientifically rich missions. By the mid-2020’s we should have another two or more new missions to look forward to.

Countdown to the Next NASA Discovery Mission Selection

2016-12-03T19:56:00.000-08:00

If NASA’s managers hold to their schedule, we will learn sometime this month what NASA’s next planetary mission will be. This will bring to a close a two-year process that saw 27 teams of scientists and engineers propose missions for the agency’s Discovery program followed by a winnowing of the field to five finalists. Out of the process should come the selection of one (and if the gods smile, two) missions that will launch in the early 2020s to study either Venus or the asteroids.

The Discovery program funds NASA’s low cost planetary missions (typically $600-700 million for all costs) to allow for more frequent missions. Nine missions have successfully flown through this program to solar system destinations as diverse as Mercury, our moon, Mars, several comets, and several asteroids. (For those who note that the next mission will be the 13^th selection, one previous mission failed, another is the Kepler telescope observing planets around other stars, and one is still in development.)

The Discovery mission finalists. Text in red refers to advanced technologies different teams propose to fly. Credit: NASA

In the first round of this competition, the agency’s managers evaluated the proposals on how compelling their science would be and on their engineering and cost feasibility. This led to the selection of the five finalists:

The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission would use an entry probe to measure the trace gases in that planet’s atmosphere to study the evolution and current state of the planet including recent volcanic activity. It would also image the surface of one of the continent-sized highlands known as tesserae.

The Lucy mission would perform flybys of several of the Trojan asteroids that share the orbit of Jupiter. These compositionally diverse bodies are believed to be remnants delivered to their current locations from across the early outer solar system. Exploring these worlds would help us better understand the range of conditions and orbital dynamics of the early solar system.

The Near Earth Object Camera (NEOCam) mission would use a space telescope to both discover new asteroids (especially those with orbits near Earth’s) and characterize a multitude of know asteroids. The results would be a massive database that could be mined to explore the range of asteroid sizes, compositions, and orbital dynamics to study these worlds as entire populations.

The Psyche mission would orbit the asteroid of the same name, which is the largest metallic world in the solar system. This body may be the exposed remnant center of a protoplanet, in which case it is our only opportunity to explore the core of a world directly. Or Psyche may be an asteroid that formed close to the early sun before later being flung into the main asteroid belt.

The Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission (VERITAS) mission would remap the surface of Venus using radar at much higher resolution than the 1989 Magellan mission. It would also conduct the first global mapping of the composition of the surface.

(In a previous post, I provided more detailed summaries of the goals of each of these proposed missions.)

The teams proposing these finalists have had approximately a year to refine their proposals. The evaluation of the final proposals is reputed to be a tough, rigorous examination looking into all the details for any flaws. Could all the science goals be met? Are there in flaws in the design or proposed testing procedures? Could the mission be implemented within budget? Do all the key personnel proposed for the mission have the experience to execute the tasks assigned to them?

The final evaluations are delivered to NASA’s Associate Administrator for Science, Thomas Zurbuchen, who will make the final decision on which mission to fly. Assuming that more than one proposal survives the technical evaluation wringer, he may include factors such as his judgement of which scientific questions are more compelling or which mission would best balance the overall planetary program (for example, NASA hasn’t launched a mission to Venus since the late 1980s but has launched three asteroid missions since then).

It is possible that Dr. Zurbuchen will announce two missions to fly. When the list of finalist proposals was announced, NASA stated that a second mission might be selected if more than one passed the final review process and sufficient funding was expected in future budgets. Choosing two missions from a single competition would make it easier for NASA to meet its goal of four to five Discovery launches per decade. (The competitions are expensive and time consuming for both the planetary community and NASA.) As recently as this summer, the head of NASA’s planetary science division said that his goal was to make the case for two selections, but statements by other NASA managers have sounded more cautious.

At least two recent events weigh, in my opinion, against a second selection. First the Discovery mission in development, the Mars InSight geophysical station, experienced development problems and will need an additional $154 million to prepare for launch. Much of that money may come from the Discovery program’s budget, reducing funds available for future missions. Second, the new president elect is promising both massive tax cuts and massive new spending on infrastructure. Affording that program may lead to severe budget cuts elsewhere in the federal budget, including at NASA. Budgetary caution may be the smart move.

While NASA’s managers likely will have found it hard to select from a field of excellent candidates, among space enthusiasts there may be a clear favorite. For the past year, my blog site has posted a poll asking readers to select their personal favorites. VERITAS was the clear favorite (48% of votes) followed by Psyche (19%), DAVINCI (14%), Lucy (9%), and NEOCAM (7%). (The poll also asked for votes for a second mission, should one be selected, and the results were similar.) I am surprised that the votes are not more evenly distributed – all the proposals are scientifically compelling. Psyche and Lucy, for example, would be missions of exploration to never before visited classes of worlds. This poll likely represents the personal preferences of planetary exploration enthusiasts (although members of the professional planetary exploration community also read the blog and may have voted), and therefore probably don’t represent the evaluation weightings that NASA’s managers will apply. (So far, over a number of mission selections, my personal favorite proposals have been selected perhaps about 25% of the time.)

In the next few weeks, we are likely to learn which of these proposals will be NASA’s newest approved mission, or missions. Whichever one is chosen, it will add significantly to our understanding of the solar system.

The Election and NASA’s Planetary Program

2016-11-14T22:09:00.000-08:00

Following the results of the Presidential election, I’m sure that many of you are wondering how planetary exploration will fare at NASA over the next few years.

The short answer is that nobody knows.

However, I can discuss some of the factors that may decide that question.

The bottom line will be how well the program is funded. Depending on how political machinations turn out, I can see situations in which the planetary program could receive substantially less, about the same, or substantially more than it does this year.

As SpacePolicyOnline nicely describes, the first key question will be whether the Republican party, which controls both houses of Congress, decides to institute major budget cuts to the overall discretionary budget. The federal budget can be described as a retirement and medical benefits system (e.g., Social Security and Medicare), the military, interest payments, and everything else (discretionary funding). Discretionary spending in Fiscal Year 2015 was approximately 16% of federal spending (the percentage for Fiscal Year 2016 would be similar). Since 1990, NASA’s share of the Federal budget has been relatively flat with a slow decline and today represents around 0.5%. If total Federal spending declines, spending on NASA seems likely to decline, too.

Source: Wikipedia

For reasons too complex to go into here (but see the SpacePolicyOnline article), one group of Republicans in the past year has wanted to institute major cuts to discretionary spending. If that happens, NASA’s overall spending number will compete for remaining funds with spending on many other discretionary items (for example, the FBI, National Parks, infrastructure spending). In this case, I think NASA’s top number would likely be cut significantly. I also think it would be unlikely that the planetary program would be spared cuts.

However, if the eventual political consensus is to keep overall discretionary spending at similar levels as recent years (true political revolutions are rare), then other political factors will matter. The first is what level of priority the new Trump government will give to NASA. So far, all we have are opinion pieces written by two people associated with the Trump campaign. The Trump administration’s actual policy will emerge in the coming months to a year or so as the new administration finally gets around to thinking about small federal agencies around which there is no major political focus. I’m sure that whatever policy statements emerge will laud NASA and proclaim lofty goals (NASA is politically like apple pie; almost everyone professes to love its mission and inspiration). Real policy, though, is stated by funding. Will the words be backed by money? Both the Bush and Obama administrations, for example, had lofty public goals for NASA – return to the moon, go to Mars – but their budgets kept NASA’s human spaceflight program firmly in low orbit. Look to the President’s proposed annual budgets rather than to speeches.

Whatever NASA top line funding number emerges, I suspect that the planetary program will retain or potentially increase its share of that budget. Exploring the solar system has had strong Congressional support, most notably from Congressman Culberson of Texas, chairman of the House Appropriations Subcommittee on Commerce, Justice, Science, and Related Agencies. In addition, based on the stated science priorities of both President-elect Trump and Republicans in Congress, the NASA’s program to study the Earth is likely to suffer major cuts and the planetary program seems likely to benefit. (For the record, I am strongly opposed to cuts to the Earth Science program. Humans are dramatically changing our planet whether you look at increases in greenhouse gasses, the nitrogen cycle, or the transformation of whole ecosystems to name but a few. Ignoring these changes is like pretending that your illness will go away if you don’t take medical tests.)

I personally expect that the status quo will persist for the coming year as the new administration and Congress settle in. I expect that we will begin to learn how NASA as a whole and the planetary program within that whole will fare starting in 2018. Given the lag in budgets and eventual mission launches, the final annual budget numbers during the next four years will determine the planetary program of the mid-2020s.

Comments

2016-09-02T07:05:00.003-07:00

For some reason, this blog has become the target of Indonesian (at least that's the language Google translate says it is) comment spanners. I have turned on comment moderation, but don't seem to be always receiving notifications of a new legitimate comments. I will log in daily to see if there are comments.

Selecting the Next New Frontiers Mission

2016-08-22T21:41:00.000-07:00

NASA’s managers have begun the process for a competition to select a new planetary mission to launch in the mid-2020s that will address one of the most important questions in planetary science. The winning proposal will be the fourth mission in the agency’s New Frontiers program that sent the New Horizons craft to Pluto, the Juno orbiter to Jupiter, and will launch the OSIRIS-REx mission next month to return a sample from a primitive asteroid.

Previously selected New Frontiers missions. Credit: NASA

NASA’s planetary missions fall into three categories of ambition and cost. At the high end at around $2-2.5 billion are the Flagship missions that use highly capable spacecraft for exploration that addresses a wide range of questions at the target world. These missions include the Curiosity Mars rover, its 2020 Mars rover sibling in development, and the planned Europa multi-flyby mission.

At the low end, at around $600 million, are the Discovery missions that conduct highly focused missions. Teams are free to propose missions to study any solar system body except the Sun and Earth (which are studied through other programs at NASA). Ten of these planetary missions have flown successfully and have included the MESSENGER spacecraft that orbited Mercury and the DAWN spacecraft that currently orbits the asteroid Ceres. Next up will be the 2018 InSight geophysical station for Mars to be followed by one or two missions to study either asteroids and/or Venus that will be selected by the end of the year.

At a total cost of somewhere around $1 billion, the New Frontiers missions fit between these two programs in ambition. The goal for these missions are to address focused high priority science questions. The scientific community selects the candidate themes through the Decadal Survey in which a long list of scientist-proposed ideas are vetted and prioritized.

The next New Frontiers mission will be selected from among a list of the six mission themes that the planetary science community identified as as highest priority to answer key questions about our solar system:

Comet Surface Sample Return – Enable in-depth laboratory analysis of the most primitive material left form the formation of the solar system
Lunar South Pole-Aitken Basin Sample Return – Enable in-depth laboratory analysis of material from our moon to understand the how the bombardment of the inner solar system worlds by comets and asteroids effected their formation
Saturn Atmospheric Probe – Determine the composition of Saturn’s atmosphere to help us better understand the formation of the solar system
Trojan Asteroid Tour and Rendezvous – Explore a reservoir of remnant bodies from the formation of the solar system to understand how materials from different regions of the early solar system mixed during planetary formation
Venus In Situ Explorer – Understand the formation, evolution, and current state of the atmosphere and surface of our sister world that evolved into a hell
Ocean Worlds (Titan and/or Enceladus) – Do these two moons of Saturn have the conditions to support life and is life present?

The first five of these themes were selected through the Decadal Survey. NASA’s managers added the Ocean Worlds theme in response to a Congressional directive and further discoveries by the Cassini mission. For the next, fifth New Frontiers competition, Jupiter’s moon Io and a lunar geophysical network theme will be added.

NASA’s managers currently expect to select a New Frontiers mission from the list of themes approximately every five years. At that pace, completing this series of investigations, including the new themes for the next selection, will require around forty years (assuming no changes to the list from future Decadal Surveys). The pressure on each proposing team to have their proposal selected now rather than waiting decades must be intense. (If this long time frame seems disheartening, some of the themes may be addressed by other space agencies. A European team, for example, is proposing a Saturn atmospheric probe to the European Space Agency. NASA Discovery missions may also partially address some of the themes. Among the five proposals competing to be among the next Discovery missions are spacecraft that would address several of the atmospheric objectives of the Venus theme and address the Trojan theme through flybys rather than the proposed New Frontiers orbiter plus flybys approach.)

For some of the themes, the Decadal Survey listed (and NASA’s managers have adopted) very specific research goals. Any team proposing a mission for the Venus in situ explorer, for example, must propose a probe that would descend through the atmosphere and likely land on the surface. Here are the objectives from the draft document announcing NASA’s request for proposals (called an Announcement of Opportunity (AO)):

The Venus In Situ Explorer mission theme is focused on examining the physics and chemistry of Venus’s atmosphere and crust by characterizing variables that cannot be measured from orbit, including the detailed composition of the lower atmosphere, and the elemental and mineralogical composition of surface materials. The science objectives (listed without priority) of this mission theme are:

Understand the physics and chemistry of Venus’s atmosphere through measurement of its composition, especially the abundances of sulfur, trace gases, light stable isotopes, and noble-gas isotopes;
Constrain the coupling of thermochemical, photochemical, and dynamical processes in Venus’s atmosphere and between the surface and atmosphere to understand radiative balance, climate, dynamics, and chemical cycles;
Understand the physics and chemistry of Venus’s crust;
Understand the properties of Venus’s atmosphere down to the surface and improve understanding of Venus’s zonal cloud-level winds;
Understand the weathering environment of the crust of Venus in the context of the dynamics of the atmosphere of Venus and the composition and texture of its surface materials; and
Search for evidence of past hydrological cycles, oceans, and life and constraints on the evolution of Venus’s atmosphere.

This is an ambitious list, and the AO specifically states that proposers can select, but must thoroughly justify their selection, a subset of these goals.

By contrast, the goals for the Trojan asteroid tour and rendezvous reflect the fact that we know very little about these never-visited bodies that share Jupiter’s orbit. This population of small worlds represent fragments left over from the formation of the planets. The diversity of the composition of these worlds will allow scientists to select from among competing models for how the solar system formed. The requirements for this theme are short:

The Trojan Tour and Rendezvous mission theme is intended to examine two or more small bodies sharing the orbit of Jupiter, including one or more flybys followed by an extended rendezvous with a Trojan object. The science objective of this mission theme is:

· Visit, observe, and characterize multiple Trojan asteroids

The briefness of the requirements for the Trojan theme likely makes life harder for teams proposing a mission to these worlds. In judging proposals, NASA’s review teams will score proposals on their scientific merit (~40% of score), the feasibility of the specific proposed instruments and measurements (~30%), and overall mission feasibility within the cost cap (~30%). Scientific merit includes an explanation of the, “Compelling nature and scientific priority of the proposed investigation's science goals and objectives. This factor includes the clarity of the goals and objectives…” Teams proposing for Venus have the benefit of goals developed and specified by the Venus science community while teams proposing for the Trojans have to develop and defend their own list of specific science goals and objectives.

(At the end of this post, I’ve copied the specific goals for the remaining mission themes from the AO.)

Missions proposed for the next New Frontiers program will need to meet many criteria including these:

Total cost for the development of the spacecraft, the instruments, and analysis of the returned data cannot exceed $850 million. NASA will separately pay for the mission’s launch and operation costs while in flight (likely several tens of millions of dollars per year), which together probably will bring the total cost of the mission to $1 billion or more.
Proposals can include instruments paid for by foreign governments, but the costs of these instruments cannot exceed one-third of the cost of the total instrument compliment. As one NASA manager put it, NASA invests a great deal of money to develop instrument technologies by American scientists, and it wants to see a return on that investment by having the majority of instruments on the selected mission be American.
Teams can propose the use of radioisotope heaters and radioisotope electrical power generators for their missions. These units would be useful for missions operating far from the sun (for example, at Saturn). However, a mission using these units would need to reserve a substantial portion of the core $850 million to cover the cost of these units. Using just the heaters would incur a cost of $47-79 million (depending on the number) and the electrical power generators would cost $133-195 million (again based on the number of generators used). These costs could drastically reduce the capabilities of the spacecraft and instruments compared to missions that don’t require these technologies.

I suspect that for many readers of this blog, a mission to return to Enceladus or Titan to continue their exploration with a new generation of spacecraft and instruments would be a personal favorite. I share that desire, but also recognize the challenges any proposal to these worlds would face. First, these worlds were just added to the list of candidate themes in the past few months. The in-depth analysis of objectives for these missions is just getting underway by the scientific community. Second, the technical maturity of instruments to explore their oceans, determine their habitability, and search for life may be low – NASA has not made major investments in these technologies for these worlds (but plans to begin to do so). And third, these missions are likely to need radioisotope power generators and their cost would eat significantly into the mission budget, potentially making it less competitive. (Solar powered missions are possible at Saturn, but appear to be on the edge technically. This could make a proposal that depends on solar power appear technically risky.) Balancing these negatives is a heritage of three Discovery-class proposals to these worlds that were not selected but which could form the basis of a New Frontiers-class mission. Still, I personally doubt that a mission to these moons will be selected this time. (If I am wrong, given a mid-2020’s launch and a flight that could last 10 years, it could be the mid-2030s before the spacecraft arrives at its target.)

I’ve learned to not try to predict which Discovery or New Frontiers mission is likely to be selected from the list of proposals made. The scrutiny given these proposals is intense. Any fault with the details of a proposal can rule it out. If the review panel decides that a proposed key engineering manager doesn’t have sufficient experience, that could kill a proposal. If the review panel concludes that a technology proposed to be used for the spacecraft or a key instrument lacks maturity, that could kill a proposal. If the review panel concludes that the specific set of scientific objectives proposed are not as compelling as for other proposals, that could kill a proposal. No matter how sexy a proposal might look from the limited information that we in the general public get to see, faults in the details that we never see may rule it out.

However, we need to remember that all the candidate themes for the upcoming selection of the fourth New Frontiers mission represent questions deemed to be among the highest priority for exploring the solar system. Whichever mission is finally selected will significantly expand our understanding of the solar system.

Schedule for the next New Frontiers competition and launch:

Final AO Release Date -- January 2017 (target)
Deadline for Receipt of Proposals -- AO Release + 3 months + 4 days
Selection of a subset (historically, two) of proposals for further study -- November 2017 (AO release + 10 months)
Final selection -- July 2019 (target)
Launch -- December 31, 2024 if solar powered or December 31, 2025 if radioisotope power sources are required
Flight time to the target world: Days (the moon), months (Venus), years to a decade or more (comet with Earth return, Saturn, or Trojan asteroids)

Science goals for the remaining mission themes (goals for the Venus and Trojan asteroid themes listed above):

The Comet Surface Sample Return mission theme is focused on acquiring and returning to Earth a macroscopic sample from the surface of a comet nucleus using a sampling technique that preserves organic material in the sample. The mission theme would also use additional instrumentation on the spacecraft to determine the geologic and geomorphologic context of the sampled region. Because of the increasingly blurred distinction between comets and the most primitive asteroids, many important objectives of an asteroid sample return mission could also be accomplished by this mission. The science objectives (listed without priority) of this mission theme are.

• Acquire and return to Earth for laboratory analysis a macroscopic comet nucleus surface sample;

• Characterize the surface region sampled; and

• Preserve sample complex organics.

The Lunar South Pole-Aitken Basin Sample Return mission theme is focused on returning samples from this ancient and deeply excavated impact basin to Earth for characterization and study. In addition to returning samples, this mission would also document the geologic context of the landing site. The science objectives (listed without priority) of this mission theme are:

• Elucidate the nature of the Moon’s lower crust and/or mantle by direct measurements of its composition and of sample ages;

• Determine the chronology of basin-forming impacts and constrain the period of late, heavy bombardment in the inner solar system, and thus, address fundamental questions of inner solar system impact processes and chronology;

• Characterize a large lunar impact basin through “ground truth” validation of global, regional, and local remotely sensed data of the sampled site;

• Elucidate the sources of thorium and other heat-producing elements to understand lunar differentiation and thermal evolution; and

• Determine the age and composition of farside basalts to determine how mantle source regions on the Moon’s farside differ from the basalts from regions sampled by Apollo and Luna

The Ocean Worlds mission theme is focused on the search for signs of extant life and/or characterizing the potential habitability of Titan and/or Enceladus. For Enceladus, the science objectives (listed without priority) of this mission theme are:

• Assess the habitability of Enceladus’ ocean; and

• Search for signs of biosignatures and/or evidence of extant life.

For Titan, the science objectives (listed without priority) of the Ocean Worlds mission theme are:

• Understand the organic and methanogenic cycle on Titan, especially as it relates to prebiotic chemistry; and

• Investigate the subsurface ocean and/or liquid reservoirs, particularly their evolution and possible interaction with the surface.

The Saturn Probe mission theme is intended to deploy one or more probes into Saturn’s atmosphere to directly determine the structure of the atmosphere as well as noble gas abundances and isotopic ratios of hydrogen, carbon, nitrogen, and oxygen. The science objectives (listed without priority) of this mission theme are:

• Determine noble gas abundances and isotopic ratios of hydrogen, carbon, nitrogen, and oxygen in Saturn’s atmosphere; and

• Determine the atmospheric structure at the probe descent location.

Red Dragon and Planetary Exploration

2016-06-06T21:32:00.000-07:00

A few weeks ago, as I’m sure most people reading this blog know, Elon Musk, the CEO of SpaceX announced plans to land their Dragon spacecraft, largely at the company’s expense, on Mars. While this plan is audacious enough, Musk has previously positioned SpaceX’s Dragon capsule as an all-purpose lander suitable to explore almost the entire solar system.

Since Musk’s announcement, I’ve been doing research and thinking about what the availability of a commercial planetary lander might mean for planetary exploration. Even if landing the company’s Dragon spacecraft on Mars proves to be a one-time event, it will demonstrate that the technologies for planetary missions have become widely available.

What if, though, SpaceX’s Dragon spacecraft becomes a standard catalog item that could ordered, the way a launch vehicle is? What might the impact be on planetary exploration? As I thought about this, I concluded that three questions are key: How flexible will the Dragon spacecraft be as a payload delivery vehicle? How far afield can it operate in the solar system without design changes so massive that it becomes necessary to essentially redesign it? And how will be missions it might fly be paid for?

Mock up of the Dragon version 2 capsule for Earth orbital missions. Credit SpaceX.

First, some background on the Dragon spacecraft. SpaceX currently is using the first version of the uncrewed Dragon spacecraft to deliver supplies to the International Space Station. It is also being being funded by NASA to design a crewed version of the spacecraft to deliver astronauts. (I couldn’t find out what proportion of the Dragon development is being funded by NASA versus by SpaceX’s own funds.) Musk has ensured that this second version incorporates key technologies such as heat shields that can survive atmospheric entry from interplanetary speeds and built in thrusters that allow soft landings. (Phil Plait at Slate magazine has an excellent article on the technologies involved. Wikipedia has additional information.)

Designing a craft for interplanetary flight requires numerous differences from a craft designed to operate in low Earth orbit for short periods of time and then return to our world. Systems must be able to function for months to years. Electronics must be able to function in the harsher radiation environment outside the Earth’s magnetosphere. The communications system must be able to transmit and receive data over distances of hundreds of millions of kilometers. There will be hours to days between communications periods, requiring the craft to be able to operate autonomously.

Artist's conception of the Red Dragon capsule on the surface of Mars. Credit: SpaceX.

To operate as a long-lived lander on the surface of a planet, the spacecraft must deploy solar panels to generate power after touch down. (I’ve not heard of any plans to use plutonium-based power generators for the Dragon spacecraft.) Batteries must be carried and recharged to keep the spacecraft operating during the night. And especially on frigid Mars, the spacecraft will need insulation and heaters to keep it warm.

These problems are well known, and we can presume that SpaceX’s engineers have designed the Dragon spacecraft and their subsystems with these issues in mind. It’s worth pausing for a moment to consider the kind of commitment this implies to SpaceX’s commitment to revolutionize Martian exploration because these enhancements likely aren’t cheap.

By making these investments in the basic Dragon spacecraft design, referred to as the Red Dragon for Mars missions, SpaceX can take advantage of what is likely to be a low volume assembly line building these craft. While NASA has designs of its own it can reuse to land on Mars, flights are likely to be infrequent enough that their components may gradually become obsolete and the expertise to rebuild and test them may fade. SpaceX presumably will be building several Dragon spacecraft a decade, allowing it to gradually update the design and keep its expertise intact. The result will likely be a lander that may be substantially cheaper than NASA reusing its existing designs for some Mars missions.

How Flexible is the Interplanetary Dragon Lander?

I know of two proposals for scientific missions that would use the Red Dragon spacecraft. One, IceBreaker, led by NASA’s Chris McKay would return to the northern polar plains of Mars to further investigate the subsurface ices found there for habitability and signs of life. The appeal of the Dragon spacecraft appears to have been its expected low cost. McKay has also proposed the IceBreaker mission using a near copy of the much smaller NASA Phoenix and InSight landers. The instruments would have weighed a few tens of kilograms, barely taking advantage of the payload that the Red Dragon could deliver. The Dragon lander (dubbed the IceDragon for this concept), however, could have carried a much larger drill than the Phoenix-derived lander, allowing samples to be collected from much further below the surface. (The one published abstract for the IceDragon mission from several years ago proposed a 2 meter drill. Technology development since then might allow much deeper drilling.)

Conceptual design for the IceDragon version of the Red Dragon capsule that could be sent to sample the icy plains of Mars' arctic regions. Human figure shown for scale. Credit: NASA.

The second proposal would be to use the Dragon spacecraft to deliver a launch vehicle to return samples directly from the surface of Mars to the Earth. This concept takes full advantage of the payload mass and volume offered by the Dragon. Other concepts proposed to return samples to Earth envision two missions. The first would land on Mars and launch a sample canister into Martian orbit. The second would retrieve the canister and perform the voyage to Earth. The large ascent vehicle enabled by the Dragon would, the proposers argue, combine these two functions to lower costs, complexity, and risk.

Unfortunately, this proposal requires that a rover already be on Mars that could deliver a canister with samples to the Dragon spacecraft. While NASA’s planned 2020 Mars rover will collect samples, it will leave them on the surface for a later rover to collect and return to an ascent vehicle. There isn’t the payload mass for the proposed Dragon mission to carry its own fetch rover and a direct-to-Earth ascent return vehicle, although it could launch samples into Martian orbit if it has to carry its own fetch rover according to the proposers.

Conceptual design for the Red Dragon used to carry a Mars Ascent Vehicle (MAV) and an Earth Return Vehicle (ERV). Credit: NASA.

There’s much we don’t know about the Red Dragon design. Will it be suited only to missions where the scientific investigations are limited to the immediate landing site where robotic arms could reach such as these two proposals? That would suggest missions to locations where homogenous conditions exist over large areas such as the polar plains of Mars.

A variation of the proposal to use the Dragon design to return samples from Mars would be to use it to return samples from different regions of the moon or from some of the larger asteroids. Since the scientists proposing lunar sample returns are interested in broad regional differences in composition, grabbing samples with an arm in the immediate vicinity of the lander would meet their goals.

However, many of the goals for lunar and Martian exploration require rovers that can reach and study or sample multiple locations across within a much larger study area. I have not seen any analysis about whether delivering a capable rover would be a feasible extension of the Red Dragon’s design. Could the Dragon design host a moderately large rover (smaller than the Curiosity rover but perhaps bigger than the Opportunity rover) and deploy it to the surface by including a large hatch and a ramp or crane?

NASA already has two current, proven designs for Martian landers. The first, used for the Phoenix and InSight missions, delivers a few tens of kilograms of instruments using a small, stationary lander. The key advantage of this platform is that it provides a soft landing, and its low stature provides easy access to the surface. The second system used parachutes and a rocket-powered skycrane to deliver the Curiosity rover to the surface (and the design will be reused for the 2020 rover). It also places up to 930 kilograms of rover directly on the surface, eliminating the need for ramps to get the rover off the lander. The landing system is also designed with the myriad of safety requirements needed for a rover/lander to use a plutonium power supply.

The Red Dragon will be able to deliver a slightly more massive payload, about 1000 kilograms. While the payload space appears large by the standards of most planetary landers, it doesn’t appear large enough to carry a duplicate of the Curiosity rover. Unlike the skycrane landing system, the payload will sit inside a large spacecraft, well above the ground. Long robotic arms or drills would be needed to bring surface samples to instruments inside the spacecraft or place small instruments on the surface. Delivering a large package such as a rover to the surface would require ramps or a crane. I expect that these problems are solvable, but they create a level of complexity that NASA’s skycrane system was invented to avoid.

Comparison of the sizes of the Dragon capsule (left) and the Curiosity rover entry and descent system. The Dragon capsule would not have the width to carry a Curiosity-sized rover, but likely could carry a smaller rover to the Martian surface. Credit: NASA.

Beyond the Moon and Mars

Musk has been quoted saying that the Dragon capsule can be used to explore almost any world in the solar system: “With Dragon launched on a Falcon Heavy, it can go pretty much anywhere in the solar system, because that’s a heck of a big rocket… Dragon 2 is capable of transporting scientific payloads to anywhere in the solar system, with a liquid or solid surface, with or without an atmosphere. So Dragon is really a crew transport and science delivery platform… Dragon, with the heat shield, parachutes and propulsive landing capability, is able to land on a planet that has higher entry heating, like Mars. It can also land on the Moon, or potentially conduct a Europa mission.”

Musk’s claim appears to touch on three separate issues. The first is whether the Falcon Heavy could propel a Dragon spacecraft to any location in the solar system. The answer likely is yes. For our moon, Mars, and Venus, the launcher will be able to send the Dragon directly to these worlds. If the Falcon Heavy cannot send a Dragon directly to Mercury or the outer planets, it certainly could launch it on a trajectory that would use Venus and/or Earth gravity assists to provide the additional velocity needed.

The second issue is whether the Dragon could land on these more distant worlds, which breaks into two parts. The first is how the Dragon capsule would kill the high approach velocity when it reaches its destination. The atmospheres of Mars, Venus, and Titan can kill much of the speed. It’s less clear to me whether the Dragon spacecraft would carry enough fuel to first brake into, say, Jovian orbit and then kill the remaining velocity to land on Europa. (A direct landing on Europa without entering Jovian orbit also would need to kill a lot of speed.) Musk’s statements suggest it could, but for now we lack details.

The third issue is whether the Dragon spacecraft could deal with the special environmental issues at various worlds. The moon and Mars are reasonably straightforward challenges both because of their proximity and their comparatively (for planetary destinations) benign environments. By contrast, while the Mercurian poles are cool, the spacecraft would need to deal with intense solar heating on the way to this world. The surface of Venus is intensely hot and has a crushing atmospheric surface pressure. Jupiter’s moon Europa sits deep within an intense, electronics frying, radiation belt. Titan’s surface is as bitterly cold as Venus’ is broiling. Landing on a small asteroid or comet may require special adaptations such as harpoons to hold the capsule on the surface. Traveling to any world beyond Jupiter will require a radioisotope generator for power (Saturn might be an exception).
It is possible to design spacecraft to handle any of these challenges. Missions have been proposed to land on each of these worlds, but using custom designs that take into account the unique challenges of each environments. Would it be cost effective to modify the Dragon spacecraft to handle the challenges of any of these worlds, or more cost effective to design a custom spacecraft?

There’s also the question of whether a prior scouting mission would be needed. For the moon and for high priority locations on Mars, existing high resolution images would allow mission planners to identify precise locations of safe terrain within otherwise rugged but scientifically interesting terrains. The same will be true for selected sites on Europa following NASA’s planned Europa Multiple Flyby mission. What about a world with only coarse resolution mapping or none at all?

Example of the rugged terrain the salt deposits of Ceres are found on. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

As a thought experiment, I considered a Dragon mission to land on the asteroid Ceres to explore the salts on the surface that have erupted from a likely (now frozen?) subterranean ocean. We have moderate resolution (35 meters) images of the surface from the Dawn spacecraft currently orbiting that world. The images of the terrain where the exposed salts are found that I’ve seen, however, appear quite rugged at 35 m resolution. And a lot of lander-killing ruggedness can hide within that scale of resolution. For assessing a potential Martian landing site, by comparison, NASA likes to have images with sub-meter resolution.
I’m sure that the Dragon capsule or its service module could physically carry a high resolution camera to scout for safe landing sites. But would the spacecraft have the precise pointing capability to accurately aim the camera and the stability to prevent image jitter? Again, solutions to these problems are well known, but is this something that would have to be added to the Dragon spacecraft?

Who Will Pay for Interplanetary Dragon Missions?

Until we know more about the capabilities of the Red Dragon capsule, it is hard to know what its advantages and disadvantages will be compared to existing lander designs. It may provide a significant cost advantage – remember that likely assembly line of Dragon spacecraft. However, the lander hardware is just one part of the cost of a mission. There is still the cost of the launch, the instruments, potentially a rover or a launch vehicle for sample return, and operations.

Even if the cost of a Red Dragon landing were free, these other costs would drive the total mission costs to several hundred millions of dollars. This puts a Red Dragon-based mission in competition for funding with all the other missions planetary scientists would like to conduct. A lunar or Martian landing mission may be selected by NASA only once a decade, and the Red Dragon may or may not be the most suitable design.

As an alternative, perhaps SpaceX will schedule a Martian landing every two years or so and will sell payload space to space agencies, universities, and even private companies to cover costs. Then the cost to any individual space agency, university research group, or company might be relatively small – a few million or tens of millions of dollars.

Or Musk may use the profits from SpaceX or a portion of his personal fortune to drive his own program of Mars robotic exploration. From his statements we know he wants to eventually take humans to Mars. Perhaps Red Dragon is a stepping stone to that grander vision.

Red Dragon is possible because of the vision and drive of its founder, Elon Musk. He made a strategic decision to build a capsule that could land on Mars as well as meet NASA’s needs in near Earth orbit. We will need to wait to learn what types of landed missions that vision will encompass and which worlds beyond Mars Musk wants to explore.

Defining the Missions for the Ocean Worlds

2016-04-08T11:28:00.001-07:00

One of the major revolutions in planetary science that I’ve seen in my lifetime is the discovery that the solar system contains not just one ocean world – our Earth – but several ocean worlds. Unlike or planet, which has its oceans on the surface, these other worlds trap their oceans beneath a surface layer of ice (or in the possible case of the asteroid Ceres, beneath a rocky shell). For several of these worlds such as Jupiter’s moons Ganymede and Callisto, the oceans appear to be locked between layers of ice and therefore would be unlikely candidates for abodes of life. For two of the moons, Jupiter’s Europa and Saturn’s Enceladus, the oceans appear to lie directly on top of a rocky core that would provide key elements needed to support life as well as energy from possible hydrothermal vents. Saturn’s moon Titan is a unique case, with seas of liquid ethane, methane, and propane on the surface and a water ocean in the interior that may or may not be in contact with the rocky core and occasionally interact with the surface. (This article and poster give more background on these worlds and their oceans.)

NASA’s managers, at the direction of Congress, have begun to put together an Ocean Worlds program to explore Europa, Titan, and Enceladus. At a recent meeting of an advisory group for NASA, the Committee on Astrobiology and Planetary Science (CAPS), Jim Green, the head of NASA’s Planetary Science Division, and Barry Goldstein, from the Jet Propulsion Laboratory, provided updates on plans to explore these worlds. In this post, I’ll report on the highlights of their talks (the presentations will be posted to this site (scroll down to the March 29-31 meeting) sometime in the future).

Europa Multi-flyby Mission

The only currently approved mission in the Ocean Worlds program is the Europa multi-flyby spacecraft. This mission, estimated to cost ~$2 billion, will orbit Jupiter and will take approximately 45 toe dips into the high radiation belts surrounding this moon to make close flybys. In between flybys, the spacecraft will have time to transmit the volumes of data it collected up close back to Earth. (This presentation gives a good overview of the mission design and science goals while this presentation summarizes the instrument payload.)

The mission is well into its design phase. At the CAPS meeting, the project manager, Barry Goldstein with the Jet Propulsion Laboratory, updated the committee members on refinements to the design.

Until recently, NASA’s managers had hoped that the main spacecraft could carry a 250 kilogram free flying daughter spacecraft to conduct complimentary studies. Ideas ranged from a simple Europa lander, to a spacecraft that would divert to flyby the volcanic moon Io, to a spacecraft dedicated to flying through any plumes ejecting material from the surface of Europa. NASA had invited the European Space Agency to propose (and pay for) a daughter spacecraft. In addition, a group at NASA’s Goddard Space Flight Center had developed a proposal for a free flyer that would swoop even lower to the surface than the main spacecraft to fly through any plumes while carrying a mass spectrometer more tuned to identifying bio signatures than the main spacecraft’s instruments.

Unfortunately, it appears that NASA has decided to drop the idea of a daughter spacecraft. I’m told that ESA’s managers determined that they had no way to fund such a spacecraft on the timeline for the Europa mission. NASA’s managers may have also decided they lacked the funding to build their own daughter spacecraft.

Dropping the daughter spacecraft opens up new possibilities for launching the multi-flyby spacecraft to Jupiter. NASA’s primary plan for sending this spacecraft on its way is the Space Launch System (SLS) that would enable a direct launch. This extremely large booster could launch the spacecraft directly to Jupiter with a flight time of 2.1 to 2.5 years. It will have sufficient heft to give the project a 33-35% mass margin, providing a cushion should the actual spacecraft as finally implemented weigh more than its designers currently think it will (which usually happens).

The SLS, however, is still in development and its reliability will only be proven through one or more future flights. In addition, this program is something of a political football, and so assuming it will be funded through development and into the time period of the Europa launch is a risk. It’s also unclear what an SLS launch would cost and whether or not the planetary science program could afford it. The project’s managers, therefore, are designing the spacecraft to also be capable of being launched on a less powerful commercial launch vehicle.

Currently that backup would be either an Atlas V 551 or Delta IV Heavy booster followed by three Earth and one Venus flybys to receive gravity assist boost that would enable the final flight to Jupiter (known as the EVEEGA trajectory). This extended looping flight would take 7.4 years to reach the Jovian system.

Dropping the 250 kilogram free flyer (plus supporting equipment on the main spacecraft) opens up an alternative launch plan. By enlarging the spacecraft’s propellant tanks to allow a large deep space maneuver to set up a single Earth gravity assist (known as the ∆v/EGA trajectory), a Delta IV Heavy vehicle could deliver the Europa mission in just 4.7 years while still providing a healthy mass margin of 34%. (For Falcon Heavy fans, NASA’s managers will consider this booster, too, once they have its final specifications, but they believe it would have similar performance to the Delta IV Heavy.)

This new launch backup is not yet an official plan as engineers and NASA’s managers examine it in more detail. If they decide they can adopt it, the net savings in flight time if the SLS launch is unavailable is 2.7 years.

The current baseline plan for launching the Europa multiple flyby mission is the Space Launch System. A new backup plan under consideration could reduce the alternative flight from over seven years to less than five years. Credit: NASA/JPL

Titan and Enceladus

The Ocean Worlds program now includes Saturn’s moons Titan and Enceladus as target worlds. Previous mission proposals were for either for expensive Flagship missions (with estimated costs of ~$1.5 billion to ~$6 billion) or the inexpensive Discovery missions (~$450 million). The former doesn’t fit within NASA’s budget and the latter appears to be too little to reach and explore these distant moons. In the past few months, NASA’s managers have opened up the intermediate cost (~$850 million) New Frontiers mission class to explore these worlds.

Science objectives for Enceladus and Titan presented by Dr. Green. Credit: NASA

At the CAPS meeting, Green presented draft science objectives for a possible New Frontiers mission to Enceladus and/or Titan along with example goals for measurements that would meet those objectives. For Enceladus, the goals relate to understanding the composition of the material within the plumes erupting from the moon’s southern pole. What are the organic molecules in the plume detected by the Cassini spacecraft, but which its instrument lacked the sensitivity to analyze in detail? Do these compounds suggest possible present life or a geological origin from hydrological activity? Does the chemistry suggest that the ocean below the icy crust has the necessary chemicals to support life?

The goals for Titan mission broke into two sets. The first related, as with Enceladus, to questions of chemistry. How are complex organic molecules created, modified, and stored in the upper and lower atmosphere and in the surface lakes and seas? Do any of these compounds suggest possible pre-biotic or even biotic origin? The second set of goals focus on the structure of the interior ocean (for example, is it in contact with the silicate core that would provide many of the elements needed for life?) and whether material from that ocean may have reached the surface (as evidenced by past resurfacing).

Previous studies have looked at a number of mission concepts to continue the exploration of these two moons following the Cassini mission. At the high end – and almost certainly outside the cost cap of a New Frontiers mission – were Titan and Enceladus orbiters and Titan balloons.

In the past two Discovery competitions, three missions to Enceladus and Titan were proposed (but not selected to fly). By law, NASA’s managers can’t reveal the results of their evaluations of these proposals – that’s proprietary information for the proposing teams who may well propose future missions in these competitive selections. However, comments by managers in public meetings have said their science was compelling and that missions to the Saturn system don’t fit within the cost cap of the Discovery program. The implication is that the higher mission costs allowed by the New Frontiers program could enable a mission to the Saturn system. These past proposals for Discovery-class missions suggest possible New Frontiers-class missions to these worlds.

Two of the Discovery proposals replaced orbiters with spacecraft that would – like the Europa multiple flyby mission –that would study these Saturnian moons with multiple flybys. The Enceladus Life Mission (ELF) would have flown through Enceladus’ plumes with two cutting edge mass spectrometers that would have studied the chemistry of the ocean’s volatiles and silicates. The Journey to Enceladus and Titan (JET) would have carried a mass spectrometer to study the volatiles in the plumes and Titan’s upper atmosphere. It would also have carried a thermal imaging camera that would have imaged Titan’s surface at up to an order of magnitude higher resolution (as fine as 25 m) than the Cassini spacecraft has done. The imager would also have imaged the sources of the plumes on Enceladus’ surface in much higher resolution than Cassini has.

A possible New Frontiers proposal might combine the ELF and JET proposals by carrying ELF’s mass spectrometers and JET’s thermal imager and conduct multiple flybys of Enceladus and Titan. Such a mission could address the composition questions posed by Green for Enceladus and Titan’s upper atmosphere. The thermal imager could address the questions of whether Titan’s surface morphology indicates that the subsurface ocean has interacted with Titan’s surface.

Possible enhancements to this type of mission might include an ice penetrating radar to study the subsurface structures of their icy shells. Or the thermal imager could be enhanced by adding an imaging spectrometer that would search for variations in the surface composition of Titan. Both of these latter ideas have been included in previous, Flagship-class mission proposals and would address the goal to better understand the structure of the interior oceans and their interaction with the surface.

Both Discovery proposals included high speed flybys of Enceladus. While these flybys are relatively easy to set up, the velocity (typically ~4 kilometers per second) could destroy any highly complex organic molecules as they impact the mass spectrometer instruments. One mission option would instead use a number of flybys of the moons Rhea, Dione, and Tethys to lower the orbit over two years to enable Enceladus flybys at ~1 kilometer per second. Affording the additional costs of two years of mission operations likely is hard in a Discovery mission proposal but might be an option that could fit within a New Frontiers budget.

The third Discovery proposal, the Titan Mare Explorer (TiME), would have landed a probe to float on one of the moon’s large polar seas. These lakes are believed to be stews that absorb and release gases into the atmosphere, receive a rain of complex organic molecules created in the upper atmosphere, and interact with the ices forming the shores and bottoms of the lakes. A future mission could replicate TiME’s goal to study Titan’s chemistry. The TiME proposed mission focused tightly on science conducted on a lake. A plusher New Frontiers mission might add instruments that could enhance atmospheric composition measurements as the probe descends to a lake landing as was proposed for a Flagship version of this mission several years back.

There is no assurance that an Ocean Worlds mission will be selected as the next New Frontiers mission, which will launch in the mid-2020s. These missions are selected through open competitions. The other missions on the candidate list – a Venus lander, lunar sample return, comet sample return, a Saturn atmospheric probe, and Trojan asteroid tour – are scientifically compelling in their own right and several may be less risky and expensive to implement. We should learn which mission is selected in 2019.

On a side note, not discussed at the CAPS meeting (at least while I was listening), is the question of international cooperation in exploring Titan and Enceladus. An obvious idea would be to combine the Titan lake lander with the multi-flyby spacecraft that could act as carrier and data relay in addition to its own scientific duties. Fitting both within a New Frontiers budget seems unlikely to me. However, other space agencies, particularly ESA, are also interested in exploring these worlds. It may be possible that NASA would provide one craft within a New Frontiers budget while another space agency provides the complimentary craft. Timing the funding for cooperative missions can get tricky (as shown by the inability of ESA to pay for a Europa mission free flyer on NASA’s schedule), but it is an obvious idea that I’m sure will be explored.

Examples measurements a New Frontiers mission to Enceladus or Titan might make to meet the science goals. Credit: NASA

An Ocean Worlds Lander

In addition to providing an update to the Europa multiple flyby mission, JPL’s Goldstein provided the first public look at the current concept for a Europa lander. In the normal progression of exploring a world, NASA would not look at detailed plans for lander until the results from a mission orbiting that world (replaced with multiple flybys for Europa) were in. However, Congress has directed NASA to add a lander to the currently planned Europa mission.

JPL’s engineers have decided to make the lander an entirely separate spacecraft from the multi-flyby spacecraft. To find the spot on this moon that best combines scientific value and landing safety, the multi-flyby spacecraft must first complete its examination of the surface. As a result, a landing would come at least two to three years after the arrival of the multi-flyby spacecraft. The lander spacecraft could either launch with the multi-flyby spacecraft and park itself in Jovian orbit while waiting for the reconnaissance to be complete or the lander could be launch later. (I’m betting on the latter. NASA’s Green described the current design state of the lander concept as “immature” and it’s not clear that NASA will receive sufficient time or funding to mature the design in time for launch with the multi-flyby spacecraft.)

A Europa lander, whose design could be used for landing on other ocean worlds, would consist of four major elements, a carrier craft that would also relay the lander's data, a solid rocket motor to slow the lander, a sky crane descent stage, and the lander itself.

The lander itself would look much like and be about the size of the Mars Pathfinder that landed on the Red planet in 1997 (but without the Pathfinder’s small rover). The lander would be encased in petals that would deploy, allowing the lander to right itself if necessary after touchdown and that could also act as “snowshoes” in case the landing is on a soft surface. A mass spectrometer and a Raman spectrometer would study the composition of the surface material, panoramic and microscopic cameras would provide context and close up images, and a geophone would provide seismic measurements. The lander would include an arm that could scoop or drill samples from the surface to deliver to the instruments. Batteries would power the lander for up to 21 days.

The proposed Europa lander would look much like and be roughly the same size as the Mars Pathfinder lander (bottom). Credit: NASA/JPL

While the initial target for this lander design is Europa, Goldstein pointed out that the design could be used to land on a number of ocean worlds including Enceladus and Jupiter’s Ganymede. (As discussed above, a Titan lander will need enter and descend through a thick atmosphere and then float on a sea. Its design is likely to be quite different.) Perhaps, if the funding gods are kind, we could see both multiple flyby missions to these moons and landers for these moons launch in the next decade or two.

Additional Material

Current launch plans for the Europa multiple flyby mission. Credit: NASA/JPL.

The proposed multiple flyby tour of Titan and Enceladus for the Journey to Enceladus and Titan (JET) mission (top) and the ground tracks below each flyby (top panel of bottom slide) and the imaging resolution for Titan and the height of the flyby through the plumes for Enceladus. Credit: JPL

Challenges to Enabling a Richer Planetary Exploration Program

2016-03-17T21:17:00.001-07:00

This week has brought to the fore two challenges for NASA’s managers as they try to enable the richest possible mix of coming planetary missions. At stake are whether the agency will be able to select two (the default is one) Discovery missions from the current competition, and whether there will be the possibility of a mission selected for Enceladus and/or Titan in the next decade.

When I write these blog posts, it is always more fun to write about the exciting science or clever engineering solutions than to write about policy. Often, however, the richness of NASA’s planetary science program hangs on questions of management and policy. Can NASA’s managers find the flexibility in spending to allow the selection of two Discovery missions? Can they find a way to incorporate new scientific discoveries and a changed political landscape (a new Congressional mandate) in between Decadal Surveys? This is not glamorous stuff, but it is the essential background to what missions we’ll see in the coming decade.

The Discovery question probably is the simpler because it likely “only” involves solving a $150M or so problem. For this low cost ($450M) program, the space agency is currently conducting a competition among five finalist mission proposals. These competitions are expensive to conduct and arduous for both the agency and the proposers. As a result, NASA’s managers would like stage the competitions no more frequently than approximately every four years. To increase the number of missions flown, the agency would like to select two missions that would be launched two years apart, allowing a total of five launches in the coming decade. (This plan assumes that each competition provides at least two proposals that after extreme scrutiny are scientifically compelling, technically feasible, and can be done within the cost cap. It also assumes that the currently planned future budgets are provided by future Presidents and Congresses.)

In the current Discovery competition, NASA’s managers will select one or two missions from among three asteroid and two Venus mission proposals. Credit: NASA

The wrench in this plan is the two-year delay in the previously selected Discovery mission, the InSight Martian geophysical station. As you’ve probably heard, the key instrument for this mission wasn’t ready in time to allow the planned launch this year. Instead, under a just announced new plan, the mission will lift off in 2018 when Earth and Mars next align for launch. As a result of the delay, the costs of launch and operating the mission that had been planned for the next two years are pushed out to 2018 to 2020. This is when NASA wants to start development on the next one or two Discovery missions. In addition, a substantial group of engineers and scientists need to be paid from now until launch in 2018 to fix the instrument problem and retain the core group needed to prepare the mission for launch and flight.

When NASA’s director for its planetary science program, Jim Green, announced the new InSight plan at a recent meeting, one of the earliest questions was whether or not this meant that NASA would still be able to select two Discovery missions. An article on the journal Nature’s website poses the same question.

NASA has not formally released an estimate of the additional costs required under the new plan, saying that those figures will be available this coming August. At a recent meeting, the InSight mission’s principal investigator stated that flying the mission later would cost $150M. It’s not clear from his statement what all is included in that figure. NASA had ~$150M budgeted for InSight for the next two years to cover launch and mission operations. Those costs will need to be shifted out two years. There will also be new costs for the 2016-2017 period to fix the instrument and to keep the core team together, and it’s not clear if this spending is included in the $150M estimate.
Because the federal budget operates on a cash basis, any money not spent in the current fiscal year returns to the treasury. So NASA can't simply bank the money it had planned to spend in 2016-2017 and spend it two years later. The agency’s managers may have some flexibility, though, subject to many rules that I don’t pretend to understand in any detail:

NASA may be able to sign long term contracts with an outside company or organization (which would include the Jet Propulsion Laboratory, which is developing and will later operate the InSight mission). In some cases, money committed to a contractor counts as spent by the government when the contract is signed but the contractor can spend the transferred money later.

NASA’s managers may be able to shift money among projects. For example, they might be able to spend money in the next two years originally earmarked for InSight on the Mars 2020 rover project. Then in 2018-2019, the agency might be able to spend money originally planned for the rover on InSight.

The $150M is less than half of what NASA is projected to be spending on Discovery mission development per year by the end of the decade. In theory, delaying the start of the next Discovery mission(s) by around six months might solve the cash flow problem and allow the selection of two Discovery missions. Jim Green has said that mission timing will be crucial, and all the teams currently in the Discovery competition have been asked to identify alternative launch dates.

I am convinced that NASA’s managers would like to fly InSight and select two new Discovery missions if fiscally possible. The kinds of options that I've mentioned above probably just scratch the surface on the kinds of ideas they are exploring. We will know more when NASA’s managers release the final budget plan for InSight this August and when they announce in late this year whether or not they selected one or two new Discovery missions.

In the meantime, veteran space reporter Jeff Foust has tweeted that Science Mission Directorate head John Grunsfeld (Jim Green’s boss) told him that the option to select two missions is still on the table. We can hope that he and his managers find a solution to select two.

The other problem, how to enable missions to Saturn’s moons Titan and Enceladus may not have such a clean path to a resolution. A spate of new discoveries have raised interest in exploring these worlds as possible abodes of life. These discoveries caught the attention of key members of Congress who have directed NASA to establish an Ocean Worlds program to explore these two moons along with Europa. (There are other ocean moons in the outer solar system, but they are less likely to be abodes of life or would be harder to explore.)

The Congressional mandate directed NASA to explore these worlds through a mixture of low-cost (Discovery program), medium cost (New Frontiers program, ~$850M), and high cost (Flagship, >$1B) missions. Planning for a Europa mission with a Flagship mission is underway (although there’s no agreement on when the mission should launch). NASA is left to find a way to send new missions to Titan and Enceladus to fulfill the Congressional mandate.

Unfortunately, neither of these moons was highly ranked as targets by the most recent Decadal Survey, which represents the consensus of the scientific community on exploration targets. (Europa was highly ranked.) The Survey examined missions to land on the lakes of Titan and decided that the scientific return for the estimated approximately $1B cost was not high enough. A mission to orbit Titan, land on a lake, and fly a balloon was estimated at an astronomical cost of $6.7B. Mission concepts, primarily orbiters, were examined for Enceladus, found to be expensive at $1.9B and were not a priority at that cost.

Fortunately, mission concepts such as multi-flyby spacecraft instead of more expensive orbiters have been more fully developed, giving mission planners lower cost options. In recent competitions for Discovery missions, two teams have proposed multi-flyby missions to fly through Enceladus’ plumes to search for clues to habitability and in one of the proposals to also map Titan’s surface at higher resolution. A third team proposed a lander for a Titan lake. All of these proposals were for missions at a fraction the cost of the Decadal Survey cost estimates for similar (but to be fair, more capable) missions.

Unfortunately, per a comment by Green at a recent meeting, while these Discovery missions proposed compelling science, they were judged by reviewers of being unlikely to fit within the Discovery cost cap. Green implied that similar missions could fit within the New Frontiers budget cap (further implying costs substantially lower than their Decadal Survey cost estimates).

Given NASA’s current budget level and missions in development, the agency has no ability to add another major Flagship mission to the queue of missions before the mid-2020s. That leaves NASA’s New Frontiers program as the only potential home for an Enceladus and/or Titan mission in the next ten years or so. But there’s a problem using this program, too. While Discovery proposals can target any world in the solar system except the Earth and sun, candidate missions for the New Frontiers program competitions were pre-selected by the Decadal Survey. The list was carefully examined to ensure that the missions are scientifically compelling, affordable, and balance the wide interests of planetary scientists. Because NASA is mandated to follow the Decadal Survey in setting its priorities, the list of recommended missions carries weight. One purpose of the list is to prevent teams from lobbying outside the Decadal Survey for their favorite New Frontiers candidates to NASA’s senior managers and Congress. (There’s no mechanism to prevent Congress from imposing its favorites on NASA, though.)

For the fourth New Frontiers competition that is in its initial stages, the Decadal Survey reports said that a mission should be selected among these candidates. Credit: NASA

For the fifth New Frontiers competition, currently planned for the early 2020s, the Decadal Survey recommended that two additional missions be added to the list of candidate missions.

NASA has just begun the process of starting the competition to select the next New Frontiers mission from among the candidates, with a target launch in the mid-2020s. The agency’s managers decided to add a mission to Enceladus and/or Titan to the list of candidate missions. Many scientists within the planetary community are not happy with this addition.

Last week, I listened in on the first day a meeting (the Planetary Science Subcommittee) of senior scientists discussing the issue with Jim Green. Their main objections boiled down to several points:

The New Frontiers current list was developed by the entire community and NASA’s managers should not arbitrarily change it. At a minimum, the addition should be vetted before the mid-term Decadal Survey review planned for next year. Doing otherwise undermines the credibility of the Decadal Surveys. Green’s response was that given the timing of the Congressional mandate and the planned start for the next New Frontiers competition, a discussion in the mid-term review wasn’t feasible. It was either now or wait for yet the next New Frontiers competition that would start in the early 2020’s. In Green’s words, the timing of the mandate sucked because it limited his ability to consult with the broader scientific community before having to tell the community what missions they could propose for the competition.

Many are concerned that rather than being an open competition, an Ocean World’s selection is pre-determined. There’s no point to teams proposing the other candidate missions. Green’s response was that NASA will run a clean competition.

Why these two moons and not Pluto or the asteroid Ceres where there have also been exciting new discoveries? Green’s response was that there are no credible New Frontiers-class follow up Pluto missions and teams have yet to propose cost-capped Ceres missions, but he expects them in the future.

At this meeting, scientists reported on discussions in analysis groups representing specific planetary science disciplines. Perhaps predictably, the report for the outer planets group was enthusiastic about the addition while reports for the small bodies and Venus groups – which have candidate New Frontiers missions – were troubled to upset by the addition. The Mars group – which has no New Frontiers candidates – was silent on the topic. The report from the lunar group – which has two candidate missions – was also silent on this topic, but this group meets the least frequently of the analysis groups and simply may not have had a chance to caucus and decide either way.

As the discussion on adding Enceladus and Titan to the New Frontiers candidate list continued, it became more nuanced. A few of the scientists wondered if an Enceladus/Titan proposal would be competitive given the lack of a mature list of scientific questions and design concepts. The Decadal Survey carefully defined the scientific goals for the missions on its candidate list. In addition, most of the missions on the New Frontiers candidate list have been proposed before or have similar Discovery proposals to draw on. Green noted that Enceladus/Titan proposals would also have Discovery proposals to draw on. He said that NASA was working on a plan to define the scientific goals for an Enceladus/Titan mission for this competition.

Green also talked more about NASA’s choices in response to the Congressional mandate. NASA’s managers could decide to consider a mission to these moons to be a strategic mandate outside of the Decadal Survey’s recommendations. The agency is planning for a Mars orbiter in the early 2020’s as a strategic mission to provide a communications relay to future missions, follow up on scientific questions raised since the last decadal survey, and prepare for future human missions. In a similar vein – and this is my speculation and wasn’t raised by Green – the agency could decide to substitute the selection of a planned New Frontiers competition in the early 2020s for a strategic Ocean Worlds mission. Instead, the agency has chosen to add a mission to the Saturn’s moons to the New Frontiers candidate list where it must beat out five other candidates on compelling science, feasibility, and cost.

NASA’s managers take the advice of the planetary science community seriously. They are actively seeking the response to their decision to add Ocean Worlds to the New Frontiers program (and at the same time selling their proposed solution). No one in the meeting I listened to stated that they questioned the scientific importance of Enceladus and Titan. However, several would appeared to believe that these two worlds should compete in the next Decadal Survey (to be released in the early 2020s) for a place as prioritized missions. NASA's managers are arguing that the time is now to recognize their priority.

This is a conversation likely to take at least a few weeks if not months to play out.

As I said at the beginning of this post, these issues aren’t glamorous. They are simply the nuts and bolts issues NASA’s managers face as they work to create the richest possible program of planetary exploration within the resources the President’s budget office and Congress provide them.

Appendix: At the Planetary Sciences Subcommittee meeting, NASA's Jim Green presented these slides to make his case that and Enceladus/Titan mission should be added to the New Frontiers candidate list. The final slide is from the Small Bodies Analysis Group (SBAG) arguing that any addition should be made follow a review by senior members of the planetary science community.

Congressional language directing the creation of an Ocean Worlds program that would include Enceladus and Titan.

Key discoveries at Enceladus since the priorities for the last Decadal Survey (in its Visions and Voyages (V&V)) priorities were set.

More Enceladus discoveries

Titan discoveries.

SBAG's statement on how new candidate missions should be added.

Proposed 2017 planetary budget: Great except for Europa

2016-02-16T19:08:00.000-08:00

It’s clear that the President’s budget officers really don’t want to fund a mission to Europa. Other than that, the proposed Fiscal Year 2017 budget submitted by the President last week to Congress would be great for planetary exploration.

The submission of the Fiscal Year 2017 proposed budget is just the opening move in getting to what will be NASA’s actual budget for next year. The proposal itself is the result of negotiations between the budget managers in the President’s Office of Budget Management and the space agency’s senior managers. Most of the proposed NASA budget is a simple continuation of the 2016 budget. In the few areas like Europa where the administration and Congress differ on policy, though, there are significant changes from this year’s budget. In the next step in the process, committees in the House of Representatives and the Senate will make changes to portions of the budget to reflect their priorities and then will negotiate their differences. Eventually a spending bill will be passed and signed by the President.

The proposed NASA planetary exploration budget would fund a fleet of current and planned missions include Discovery and New Frontiers missions expected to be selected in the next few years and several CubeSat missions (latter three not shown).

Excepting Europa (more on this later), there’s a lot to like in the proposed planetary budget. Following successive years of cuts early in the decade and a gradual series of increases to rebuild the program, the top number for the FY17 planetary program is proposed to be $1.52 billion. With the proposed cut to the Europa mission studies, this number is down by $110 million from this year’s FY16 budget.

The $1.52 billion would:

Fully fund the continued development of the 2020 Mars rover and support the selection and development of new missions for the low-cost Discovery program and the mid-cost New Frontiers program.
Fully fund all missions currently in flight or operating at their target worlds. Unlike the previous couple of years, the budget doesn’t propose to end the Mars Opportunity rover or the Lunar Reconnaissance Orbiter missions.
Provide slight increases for the programs that fund planetary science research and develop technology to be used in future missions.

With the proposed budget, we should see a number of new planetary missions launch in in the 2020s starting the launch of the ~$2.2 billion Mars 2020 rover.

If the funding levels suggested for the beginning of the 2020s were continued through the next decade, then NASA should be able to launch several low-cost (~$450 million) Discovery missions. The budget proposal specifically talks about the desire to select two missions from the Discovery competition in progress to launch in 2021 and 2023. The head of the Planetary Science Division, Jim Green, has said he’d like to hold competitions approximately every four years and select two missions from each competition, resulting in a new mission approximately every two years. That would support the launch of around five Discovery missions in the 2020’s.

The budget supports the launch of a mid-cost (~$850 million) dollar New Frontiers mission in the mid-2020s. Dr. Green has said that he and his managers are planning for launches approximately every five years going forward, meaning that we should see two missions fly in the 2020’s.

NASA also plans to regularly fly several low cost (a few million dollars each) of the cereal box-sized CubeSat spacecraft to lunar and planetary destinations.

The budget would also fully fund NASA’s contributions to the European Space Agency’s 2016 ExoMars Trace Gas Orbiter, 2018 ExoMars rover, and the JUICE Jupiter system mission that will arrive in the late 2020’s.

NASA has also talked about a new orbiter for Mars for the early 2020’s, although the budget is silent on funding for this mission.

And then there’s the Europa multi-flyby (previously called the Europa Clipper) mission. While previous Presidential budget proposals have called for this mission to launch in the mid to late 2020’s, this budget proposal seems to call for a possible delay in that vague schedule by suggesting a “launch as early as the late 2020s”. The proposal ignores language in the FY16 budget law (which governs spending only for this year) inserted by Congress directing NASA to launch the mission by 2022 (and that also directed NASA to add a lander to the mission, which also is ignored in this new budget proposal).

The stark difference between what the President’s budget proposes and what would be needed to launch the Europa mission in 2022 is shown by the numbers in the following table (both sets of numbers are provided in the budget proposal document).

	FY17	FY18	FY19	FY20	FY21
Proposed spending	$ 49.6M	$ 24.2M	$ 65.2M	$117.5M	$236.5M
Required to launch in 2022	$194.0M	$272.0M	$456.0M	$678.0M	$482.0M

Under the President’s proposal, $493 million would be spent on the Europa mission through 2021 versus the $2.1 billion needed to keep the mission on track to launch in 2022.

In political terms, pushing the mission’s launch out a dozen or more years may be the equivalent of postponing it forever. For the mission to fly, it would need continuous support from at least two more Presidential administrations and as many as six to eight new Congresses. It’s hard to imagine any mission sustaining support for that long. It’s also hard to imagine how NASA could keep a high caliber engineering and science team together for what might be fourteen or more years (with a possible six or seven additional years of flight following launch to arrive at Europa). On a very practical engineering level, many of the technologies available to design into a mission today will be obsolete and no longer available by the late 2020s. The mission design would need to be continuously tweaked to substitute new technologies.

Why might the President’s budget officials be opposed to the Europa mission? The explanation given in the proposal document is that launching a Europa mission before the late 2020’s would lead to an unbalanced planetary program that would not support the program laid out in the last Decadal Survey. This statement assumes that the cap on the total planetary budget would remain fixed at around the $1.5 billion proposed for this year.

Here are the possible explanations I’ve been able to think of for the Administration’s lack of support for the Europa mission (the first two are consistent with the explanation in the budget document):

Delaying the Europa mission prevents a bulge in spending requirements. For the rest of this decade, NASA’s new mission spending is dominated by the expensive Mars 2020 rover. The budget proposal also shows sharp budget increases late in the decade for the Discovery and New Frontiers programs. Launching the Europa mission by 2022 as mandated by Congress would require either greatly increasing overall planetary funding or cannibalizing other programs. (Note: I would like to see a much larger planetary budget.)

The budget officials (and perhaps NASA’s senior managers) prefer cheaper Discovery and New Frontiers missions to the Flagship Europa mission. Experience has shown that large Flagship mission are more likely to have large cost overruns that play havoc with NASA’s budget. Countering this, the generous money that Congress has provided the mission so far as matured the design much more than is typical at this stage of development. That maturity makes cost overruns less likely.

Europa isn’t Mars, and studying and eventually getting humans to Mars is NASA’s current overriding goal.

Pure politics. Several of the Congressional leaders who are strongly backing the Europa mission and planetary exploration in general are highly conservative politically. While they favor spending more money on planetary missions, they also want to cut funding for missions for NASA to study the Earth, especially climate change. Essentially proposing to push out the launch of a Europa mission to forever may be part of a hardball negotiating tactic to trade more funding for the Europa mission for also fully funding the President’s generous proposed budget for Earth science missions.

At the moment, we are left with the Europa mission as a formally approved mission on NASA’s books with an engineering and science team, a selected suite of instruments, and no target launch date. The interesting politics will be whether or not Congress forces the addition of the many hundreds of millions of dollars into NASA’s planetary budget over the next several years needed to launch as early as 2022 without cannibalizing other planetary programs. (For more on this, see this previous blog post.)

The Europa mission isn’t the only areas in which the Administration and Congress disagree on NASA budget and policy. While outside the scope of this blog post, they also disagree on the amount that should be spent on Earth science (as noted above), developing commercial launch capabilities, and developing the Orion and Space Launch System programs.

Outside of these areas, though, there is a consensus on spending levels, and the final budget is likely to be similar to the proposed budget.

SpacePolicyOnline has a very good summary of the overall NASA budget and areas where the Administration and Congress are likely to disagree. For the planetary program, Casey Dreier at the Planetary Society has good commentary on the proposed planetary budget.

Budget Details

Each budget proposal comes in two parts. The first proposes spending for the next fiscal year (FY17 in this case) and is the starting point for the eventual law allocating funding for the next year. The second part projects notional funding for four additional years (FY18 to FY21 in this case). These notional budgets are not acted on by Congress, but provide agencies with guidance for future years. For agencies like NASA whose projects typically take several years to implement, these notional budgets take on particular importance. The agency cannot issue multi-year contracts that are inconsistent with the notional out year budgets. These creates a problem if, for example, Congress provides generous funding for the Europa mission next year but the notional budgets are inconsistent with the necessary multi-year contracts.

The numbers for the following charts come from NASA’s budget documents except as noted.

The FY17 budget proposal projects a onetime significant increase in the Earth Science budget to pull in development of the next Landsat Earth observing satellite. The dip in planetary science funding comes primarily from proposed reductions in funding for the Europa mission. Otherwise, the budget proposal shows relatively flat projected budgets for NASA’s science budgets.

This chart shows projected budgets for budget proposals since 2010 (which proposed the FY11 spending) compared to actual allocated budgets. For the first several years of the decade, the budgets proposed reduced planetary spending, reflected in cuts in actual spending. Since the FY14 budget proposal, projected budgets have been increasing.

Within NASA’s planetary program, the budgets that fund current and future missions show projected shifts in future years as development of the Mars 2020 rover mission nears completion. Funding shifts to the low-cost (~$450M per mission) Discovery program, the mid-cost (~$850M per mission) New Frontiers program, and the outer planets program, which includes the Europa mission. Final funding levels at this level of detail haven’t been set for FY16, and I show estimates in this chart and the next from Casey Dreier and Jason Davis with The Planetary Society.

NASA’s planetary budget also includes two essential programs that funds scientists to analyze the data returned by NASA’s planetary missions and to develop technology for future missions. The latter is proposed to take a one-time hit to reflect a cut in spending to develop technology for future Europa missions. Otherwise, both programs are projected to have approximately flat funding for the remainder of this decade.

Europa Budget Bulge

2016-01-22T04:49:00.000-08:00

Casey Dreier with The Planetary Society made substantial contributions to this post.

In the children’s book, The Little Prince, there is a delightful drawing of a boa constrictor that has a bulging stomach because it swallowed an elephant. In the coming year, I believe that the key development for NASA’s mission to Europa will be an agreement on how the agency plans to accommodate the monetary bulge that will come from funding this mission. The results of the negotiations between the agency’s managers, the President’s budget managers, and Congress likely will determine when this and other new missions will fly in the coming decade.

(I had hoped to include the drawing from the book, but it appears that the copyright is still in effect in the United States and France. You can see it at this webpage or a picture of a real constrictor after it swallowed a goat on this page.)

Summary of the planned Europa multi-flyby mission from a 2013 presentation. This chart is the only one I know of that provides a cost estimate from an independent review. The official budget for the mission has yet to be established and may differ from this estimate. Since this slide, the actual instrument payload has been selected and Congress has mandated that the mission also carry a Europa lander.

So why does the boa-elephant analogy work for understanding the funding for the Europa mission? Think of NASA’s planetary science budget as a hose – or snake if you prefer – that’s of relatively similar width from year to year (except for the attempted 20% cut 2013, but that’s another story). Generally, the overall amount of money available to fund all future and existing planetary missions is relatively consistent over the near future.

But when you’re building a spacecraft, your funding needs are not consistent year to year. Over the course of the development, costs grow substantially, peak, and then tail off. In the first years of developing a mission, spending is lower as much of the work is designing and validating technology needed for the spacecraft. Spending rapidly increases as parts are built, greater numbers of engineers and technicians are assigned the project, and pieces are assembled and tested. Most projects actually peak in funding needs a year or two before they launch, creating the equivalent of an elephant’s bulge in a boa constrictor. Spending typically drops before launch, finally reaching a low and steady pace that represents the costs of operating the mission in flight.

Because the overall amount of funding available for new missions is generally flat, NASA’s project managers carefully stagger the development of new missions in order to prevent different projects from peaking at the same time.

The actual and planned spending for planetary missions in development this decade showing the characteristic bulge in spending in the years leading up to launch (2016 for the OSIRIS-Rex asteroid sample missions, was to have been 2016 for the InSight Mars geophysical station, and 2020 for the Mars 2020 rover). As the development funding bulge for one mission ramps down, the bulge for the next mission can ramp up without creating the need for wide swings in the overall Planetary Science Division’s budget. Figures are from actual budgets through FY16 and are the projected funding from the FY16 budget proposal.

For the last several years, Congress and NASA have sparred over when the Europa mission should be staggered in respect to other missions. Supporters in Congress want to see the mission launch by 2022, and are willing to increase the overall funding available to Planetary Science to help incorporate the Europa bulge. NASA has only committed to sometime in the to the mid-to-late 2020s, and has shown little desire to increase overall funding to planetary science. To efficiently develop the Europa mission, the two will have to reach an agreement on a funding plan and launch date.

If a Europa mission is to launch by 2022, its funding peak will occur around the same time as the funding peak for the Mars 2020 rover, NASA’s other major planetary mission. NASA’s Mars 2020 rover and Europa missions are both Flagship missions with an expected cost of around $2 billion. Congress, however, has stated that the Europa mission must utilize the Space Launch System booster (cost unknown) and include a lander that could add upwards of $700M to the mission’s total cost. The net result is that Congress has mandated two large simultaneous bulges be funded at once for the 2020 rover and Europa mission.

Absent an increase in the budget for the Planetary Science Division in the late 2010s, these large missions could crowd out other, smaller missions. Both Congress and the White House have shown interest in ramping up the low-cost Discovery program over the next few years in an attempt to restore the cadence destroyed by cuts earlier in the decade. There is also the next New Frontiers mission, a medium-class planetary spacecraft that would launch by 2024. The funding bulges for these missions could overlap those of the Mars 2020 and Europa missions, creating more competition for funding.

To achieve everyone’s goals would require an increase of funding for NASA’s Planetary Science Division significantly above what the White House has proposed in recent years.

Jason Callahan and Casey Dreier of The Planetary Soceity have estimated what future NASA planetary budgets might look like if all the missions planned for development in the next few years are budgeted. The result is a substantial increase over the current planetary budget for Fiscal Year 2016 of $1.63B.

First, some background. Unlike Congress, which only appropriates money on an annual basis. Budgets proposed by the President’s budget officers (in consultation with NASA’s managers) project out five years, with the first year the actual request for the next year’s funding from Congress and the subsequent years being notional, but indicative of the agency’s planning. For NASA to issue the multi-year contracts needed to develop a mission, there has to be a clear, long-term commitment from the agency that is reflected in the official budget request. It is very rare for a spacecraft to successfully come to fruition without appearing in the official President’s budget.

We will soon see if there is agreement for the Planetary Science budget to increase to accommodate this new mission. The President’s FY2017 budget request will be released in early February, we will see if it contains the larger proposed funding to include a Europa mission launch in the early 2020s.

But if the overall budget of planetary science doesn’t increase, there are several alternatives that the Administration could pursue:

Delay the launch of the Europa mission to the mid-2020’s to push out its spending bulge well after the Mars program needs
Delay the smaller Discovery and New Frontiers missions and use that funding for Europa, which would result in an unbalanced planetary program with just two Flagship missions launching in the next decade. And this wouldn’t provide all the funding needed for the two Flagship missions.
Take the additional funding from elsewhere in NASA’s budget (which would result in either hurting the human spaceflight program that has strong political backing, or hurting one of NASA’s other science program such as the Earth Science program (the latter of which has been proposed by various members of Congress, but which I oppose – we are rapidly modifying our planet and need satellites to identify and monitor the changes))

Any of these alternatives represent solutions typical of those made in budget negotiations, which assume a flattish overall budget with the individual line items being traded off.

I’m hoping that this year represents a new possibility. The public has repeatedly shown its interest in planetary exploration through its avid following of missions in the press and the internet. Congress has noticed that interest and been willing to support increases in the NASA’s planetary program for several years. Several key members of Congress also are personally interested in planetary exploration specifically and space science in general and have consistently added money for Europa over the past few years. Congress has also consistently increased NASA’s budget since 2013, providing a surprising (and welcome) 7% increase in 2016.

This seems to be the year to attempt to create a political consensus for a new, higher spending rate for NASA’s planetary program. The set of proposed missions is compelling. Congress is willing. For the next year, before the next President changes the players with the resulting delay in dealing with new policies, we have stable management teams in the President’s budget office and at NASA. And public interest groups like the Planetary Society have shown that they can demonstrate the public’s support for increased funding and build the political case for the needed funding.

These budget issues aren’t unique to the Europa mission. They occur with any large mission as NASA’s budgets are planned. In a zero-sum game, something has to give. In recent years, though, Congress has shown its willingness to increase the size of the budget to match the vision. Perhaps it will be possible to have a dream line of up missions in development: Mars 2020, Europa, two or more Discovery missions, and a New Frontiers mission. It’s worth working for.

Appendix: Estimated Europa mission costs

I have seen just one official cost estimate for the Europa multi-flyby mission (previously called the Europa Clipper) in a mission definition update. That estimate was for $2.1B without the launch (and was made by the Aerospace Corporation, which NASA uses to provide independent mission cost estimates). To estimate total spending that must be done before a possible 2022 launch, we need to add in the possible costs of the newly required Europa lander and the launch vehicle. We should also subtract the costs of post launch operations (which seem to run $50M to $70M a year for Flagship missions) and money already spent or appropriated through FY16.

Here’s what the budget swag looks like:

+$2.1B Multi-flyby spacecraft

+$0.5B SLS launch vehicle*

+$0.7B Europa lander*

-$0.3B Post launch operations*

-$0.4B Already spent/appropriated

This back of the envelope calculation results in approximately $2.6B remaining spending before launch. If launch is in 2022, then that leaves six years after FY2016, for an average spending rate of $440M per year. More likely, there will be a higher peak spending rate for a couple of years with lower spending in the beginning and end of this period (based on spending patterns of other missions). A possible average, though, is as far as I can push this thought experiment.

*SLS cost estimate from another Europa mission presentation; lander costs from a press account and may not be firm; operations costs assume a five year prime mission at a swag of $60M per year.

New Frontiers Mission #4

2016-01-07T18:05:00.000-08:00

I plan to do several blog posts on the New Frontiers 4 selection, and the list of missions that can be proposed. For now, though, here's a brief summary of NASA's announcement plus the text of the announcement.

Big News: A mission to Titan/Enceladus has been added to the list of missions that scientists can propose:

Comet Surface Sample Return,
Lunar South Pole-Aitken Basin Sample Return,
Ocean Worlds (Titan and Enceladus),
Saturn Probe,
Trojan Tour and Rendezvous, and
Venus In Situ Explorer

Selection in spring 2019, launch in 2024 or 2025. Up to three MMRTGs available.

Text of the announcement:

Community Announcement Regarding New Frontiers Program Announcement of
Opportunity

Estimated Release of draft AO .....................………...July 2016 (target)
Estimated Release of final
AO.....................................January 2017 (target)
Estimated Proposal due date........................................90
days after AO release

This community announcement is an advance notice of NASA’s Science
Mission Directorate (SMD) plan to release a Draft Announcement of
Opportunity (AO) for New Frontiers Program mission investigations with
a target release date of July 2016.

The New Frontiers Program conducts Principal Investigator (PI)-led
space science investigations in SMD’s planetary programs under a
not-to-exceed cost cap for the PI-Managed Mission Cost (PMMC). At the
conclusion of Phase A concept studies, it is planned that one New
Frontiers investigation will be selected to continue into subsequent
mission phases. There will be no Missions of Opportunity (MO)
solicited as part of this AO. All MOs are now solicited through the
Stand Alone Mission of Opportunity Notice (SALMON) AO. New Frontiers
Program investigations must address NASA’s planetary science
objectives as described in 2014 NASA Strategic Plan and the 2014 NASA
Science Plan. Both documents are now available
athttp://science.nasa.gov/about-us/science-strategy/.

Investigations are limited to the following mission themes (listed
without priority):

Comet Surface Sample Return,
Lunar South Pole-Aitken Basin Sample Return,
Ocean Worlds (Titan and Enceladus),
Saturn Probe,
Trojan Tour and Rendezvous, and
Venus In Situ Explorer.

Five themes are described in the Planetary Science Decadal Survey.
The Ocean Worlds theme for this announcement is tentatively focused on
the search for signs of extant life and/or characterizing the
potential habitability of Titan or Enceladus. The draft AO will
fully elucidate information on the mission themes.

The time frame for the solicitation is intended to be:

Release of final AO...........................................January
2017 (target)
Preproposal conference...................................~3 weeks
after final AO release
Proposals due ...................................................~90
days after AO release
Selection for competitive Phase A studies....November 2017 (target)
Concept study reports due...............................October 2018 (target)
Down-selection .................................................May
2019 (target)
KDP B .................................................................August
2019 (target)
Launch readiness date ....................................2024

PI-Managed Mission Cost (PMMC) for investigations are capped at a
Phase A-D cost of $850M (FY 2015$) with exclusions as noted in this
announcement. The now-standard 25% minimum reserve on Phases A-D will
be required within the PMMC. Operations costs (Phase E and F) are not
included in the PMMC, but will be evaluated for reasonableness. This
exclusion for operation costs will not apply to the development of
flight or ground software, ground hardware, or testbed development or
refurbishment that occurs after launch. These activities will be
considered deferred Phase C/D work and their costs will be included
under the PMMC. Only costs related to spacecraft operations will be
excluded from the PMMC. Lower-cost investigations and cost-efficient
operations are encouraged.

Launch Vehicle costs and procurement will be the responsibility of
NASA. A standard launch performance capability will be defined and
provided as GFE and its cost will not be included in the PMMC. The
cost of mission specific and special launch services, such as for
higher performance launch vehicles or the use of nuclear materials,
are the responsibility of the PI and must be included within the PMMC.
Details of these costs are still under discussion.

The value of foreign contributions remains constrained as was done for
the recent Discovery Program AO. The total value of foreign
contributions may not exceed one-third of the PMMC, and the value of
foreign contributions to the science payload may not exceed one-third
of the total payload cost.

Investigations may propose the use Multi-Mission Radioisotope
Thermoelectric Generators (MMRTG) and Radioisotope Heater Units
(RHUs). Some of the costs for the use of these systems and materials
will be included in the PMMC as detailed below. These costs are not
final and may change.

Up to three MMRTGs are available at the cost of $105M for one unit,
$135M for two units, and $165M for three units. The cost for the
unit(s) is included in the PMMC. In addition, the usage of MMRTG(s)
requires delaying the LRD by at least one year to no earlier than 2025
to allow for mission-specific funding to support provision of MMRTGs.
43 RHUs are available as GFE, and the cost of the units is not
included in the PMMC. However, the PMMC will include approximately
$26M of costs associated with the use of RHUs.

In addition to the costs above, investigations using either MMRTGs or
RHUs will also incur approximately $28M or $21M, respectively, in
costs for special launch services against the PMMC.

NASA will provide incentives for technology infusion into New
Frontiers investigations. NASA is considering providing technologies
as Government-Furnished Equipment (GFE), including up to 43 RHUs and
the NASA Evolutionary Xenon Thruster (NEXT) ion propulsion system (two
flight model power processing units and two thrusters). NASA is also
considering providing an increase to the PMMC cap for investigations
utilizing the Heat Shield for Extreme Entry Environment Technology
(HEEET), a woven Thermal Protection System. In addition, NASA is
considering limiting the risk assessment of certain technologies to
only their accommodation on the spacecraft and the mission
environment.

This incentivized technology list is not complete, and decisions on
the specific technologies and the nature of their associated
incentives will be made before the release of a draft AO. A
Technology Workshop will be held in early 2016 to provide technology
developers a chance to provide detailed information to proposers. All
NASA-incentivized technologies will participate in this workshop, but
other participants will be welcome as well.

New Frontiers Program investigations involving entry, descent, and
landing (EDL) into the atmosphere of a Solar System object (including
the Earth) shall include an Engineering Science Activity, to be funded
outside of the cost cap, to obtain diagnostic and technical data about
vehicle performance and entry environments. Details of the goals and
objectives of this activity will be posted on the New Frontiers
Program Acquisition Website (http://newfrontiers.larc.nasa.gov/) in
the Program Library.

New Frontiers Program investigations may propose activities that have
the potential to broaden the scientific impact of investigations as
optional Science Enhancement Options (SEOs). SEOs include, but are
not limited to, guest investigator programs, general observer
programs, participating scientist programs, interdisciplinary
scientist programs, and archival data analysis programs. NASA is
considering allowing New Frontiers Program investigations to also
propose Technology Demonstration Opportunities (TDOs) to demonstrate
new capabilities. TDOs and SEOs are funded outside of the PMMC cap
and may possibly not be selected even if the parent mission is
selected for flight.

NASA will release a draft of the New Frontiers AO in the summer of
2016. The draft AO will be based on the recent Discovery AO, as well
as the Standard PI-led Mission AO Template. NASA has begun its
regular assessment and revision of the Standard AO, and, once it is
complete, the Draft New Frontiers AO will be written and provided for
public comment. Proposers should read the Draft New Frontiers AO
carefully when it is released.

NASA has not approved the issuance of the New Frontiers AO and this
notification does not obligate NASA to issue the AO and solicit
proposals. Any costs incurred by prospective investigators in
preparing submissions in response to this notification or the planned
Draft New Frontiers AO are incurred completely at the submitter's own
risk.

Further information will be posted on the New Frontiers Program
Acquisition Page at http://newfrontiers.larc.nasa.gov/ as it becomes
available.

Questions may be addressed to Dr. Curt Niebur, New Frontiers Program
Lead Scientist, Planetary Science Division, Science Mission
Directorate, NASA, Washington, DC 20546; Tel.: (202) 358-0390; E-mail:
curt.niebur@nasa.gov.

European Contribution to NASA's Europa Mission

2016-01-06T06:04:00.001-08:00

Spaceflight Now has an article on the interest of European Space Agency managers of making a major contribution to NASA's Europa mission. What the article lacks is a statement of whether or not there is sufficient mass margin in the mission to carry both the newly mandated NASA Europa lander and a European contribution. It's possible that NASA doesn't yet know since it has been examining the lander concept, at the request of Congress, for only a few months.

If NASA concludes that there is mass for a European contribution, teams of scientists can propose concepts for the next ESA medium class mission selection. The competition will be tough with with other teams likely to propose a number of other compelling astrophysics and planetary mission concepts.

A Lander for NASA’s Europa Mission

2015-12-29T21:38:00.000-08:00

“This Act includes $1,631,000,000 for Planetary Science. Of this amount, $261,000,000 is for Outer Planets, of which $175,000,000 is for the Jupiter Europa clipper mission and clarifies that this mission shall include an orbiter with a lander that will include competitively selected instruments and that funds shall be used to finalize the mission design concept with a target launch date of 2022.”

“…$175,000,000 is for an orbiter with a lander to meet the science goals for the Jupiter Europa mission as outlined in the most recent planetary science decadal survey. That the National Aeronautics and Space Administration shall use the Space Launch System as the launch vehicle for the Jupiter Europa mission, plan for a launch no later than 2022, and include in the fiscal year 2017 budget the 5-year funding profile necessary to achieve these goals.”

- Final budget law for Fiscal Year 2016 regarding NASA’s Europa mission

While there’s at least eight years until it launches, this has been a pivotal year for developing NASA’s Europa mission. Last spring, NASA selected a rich and highly capable instrument set. This summer, following a design concept review, the mission moved from concept studies to an official mission. And just last week, Congress directed NASA to expand the mission by adding a small lander as well as launch the mission by 2022 and use the Space Launch System. These latter aren’t just suggestions: they are the law.

There’s been almost no official information on the lander. What we know comes from a long article from Ars Technica’s Eric Berger on the then possible addition of a lander and a dedicated plume flyby sub-satellite. Berger is a long time space reporter and has developed a good relationship with House Appropriations Subcommittee Chairman John Culberson (R-TX). (I make sure I read all of Berger’s articles.) As Berger describes in detail in his article, Culberson has been the driving force behind the aggressive funding for this mission.

In addition to an earlier launch, .Culberson also has wanted to see the mission carry a lander in addition to the mother craft that would make at least 45 close flybys of the moon. In prior years, Culberson added funding to NASA’s budget specifically to study a lander option, and the Jet Propulsion Laboratory’s engineers have been studying options. Berger’s story is focused more on Culberson, but it does provide a number of facts about the possible design for the lander:

The leading concept for the lander would be a small lander, perhaps about 230 kg with 20-30 kg for instruments. For comparison, the 1996 Mars Pathfinder lander had a mass of 265 kg.

The lander would be delivered to Jovian orbit by the main spacecraft and then released in a high parking orbit well outside the intense radiation fields at Europa’s orbit. The main spacecraft would study Europa’s surface for two to three years during its flybys to find the best combination of a scientifically interesting and safe landing spot.

The actual landing would use the same skycrane approach used by the Curiosity Mars mission to deliver the lander safely to the surface.

The lander would likely last perhaps 10 days on the surface using battery power. During the lander’s lifetime, it would investigate the chemistry of the surface using a mass spectrometer and possibly a Raman spectrometer.

A lander could add $700M or more to the mission cost. The last cost estimate I heard for just the main spacecraft was $2.1B. We don’t know how firm the lander cost estimate is.

Adding a lander would delay launch from a possible 2022 to 2023.

This description is pretty bare bones, but with a little legwork, it is possible to flesh out these ideas with some informed speculation. It helps that a number of previous studies have been published that examined concepts for a Europa lander.

In the mid-2000s, NASA studied a small Europa lander that would have had similar mass and capabilities to those reportedly be considered for the approved Europa mission. Credit: NASA/JPL.

The primary goal of any lander would be to sample material from the interior ocean to see if the chemicals needed to support life are present and whether complex organic molecules suggesting biotic or pre-biotic activity exist. We lack the technology to drill through the kilometers of ice to reach the ocean directly. However, in many locations the icy shell appears to be fractured and water from below has spilled onto the surface and frozen and in certain locations may be actively venting into space. The goal will be to set the lander down in one of these zones.

Our current knowledge of Europa’s surface is too poor to select the scientifically most interesting sites that are also safe to land in. The main spacecraft will spend three years circling Jupiter and flying low over Europa 45 times. One of its prime goals will be to for its cameras and spectrometers to find the optimal combination of evidence of ocean material on the surface with a safe landing zone. Any landing will need to wait for scientists to build their high resolution maps.

One aspect of this proposed lander concept is different than those I’ve seen before. Most lander studies have looked at small spacecraft (and this proposal would count as a small spacecraft) that would be carried by the mother craft until just before landing. For the design Berger reported on, lander and its descent stage would orbit Jupiter on their own for months to years before landing. This means that together they are a fully functional independent spacecraft with its own solar arrays for power, propulsion, navigation, and communications. Apparently the cost and mass of adding these functions to the descent stage and lander is a better bargain than adding the radiation hardening that would be required if the lander were carried past Europa 45 times.

Once on the surface, the lander could be well protected from radiation. The rotation of Jupiter’s magnetosphere causes the radiation to slam into Europa’s trailing hemisphere. The leading hemisphere has Europa’s bulk as a very effective radiation shield, and radiation there is fairly low. Past proposals have focused on putting a lander on the leading hemisphere. As a result, the lander likely would run out of power before radiation would fry its electronics. Fortunately, there are several regions on the leading hemisphere where the icy shell appears to have been recently (in geologic terms, anyway) fractured.

Berger’s article states that the lander likely would be powered by batteries, limiting its life to around 10 days. Solar panels apparently are being considered, but I can see why they might not be attractive. Sunlight at Jupiter is weak, and solar panels large enough to harvest a meaningful amount of that light might be too bulky and heavy for the mission.

Berger’s article lists just two possible instruments for the lander. Based on his language, the core instrument would be a mass spectrometer that would “weigh” the molecules and atoms in samples scooped, cut, or drilled from the surface. Extremely complex molecules could suggest life, especially if they are rich in elements, like carbon, which are the basis for life on the Earth. A second instrument under consideration would be a Raman spectrometer that would illuminate samples with lasers and use the resulting “glow” to measure composition including complex organic molecules. (For those who understand Raman spectroscopy, please forgive this simplification of a complex subject; here’s a link to a Wikipedia article for more on this technology.) I’ve also heard through other sources that the lander would carry an imager to examine the terrain around the landing site.

Once on the surface, the lander would use a sample acquisition system to collect a sample of ice from the surface. As Berger points out, at Europa’s surface temperatures, the ice is as hard as rock, so the cutting or drilling mechanism will need to be robust. After the sample is collected, it would be delivered to the instruments to measure its composition. If the lander touches down near an active vent, the mass spectrometer could also measure the composition of the particles and gases in the plume.

Previous studies typically have proposed at least two other instruments. Europa’s icy shell is constantly being stressed by the tides induced by Jupiter which should produce high seismic activity. A seismometer would give scientists a rich data set on the interior structure of the ice. Europa also sits within Jupiter’s intense magnetosphere which causes an induced magnetic field in the moon’s interior ocean. How this induced field varies as Europa orbits Jupiter would provide valuable clues to the size and salinity of the ocean. A magnetometer on the lander could provide continuous measurements for the life of the lander. Berger’s article was silent on whether or not these instruments are under consideration for this version of the lander.

(On a side note, a magnetometer plus a simple plasma probe would allow the lander to conduct useful science while it orbits Jupiter waiting for landing. Scientists would like to study Jupiter’s magnetosphere from multiple locations at once. The lander while in orbit around Jupiter could complement similar measurements from the main spacecraft, and depending on the timing, also from Europe’s JUICE spacecraft that will enter Jovian orbit in the late 2020s.)

Berger’s article is silent on how data would be returned to Earth. Two possibilities are obvious – low data rate transmissions directly from the lander to Earth or high data rate transmissions from the lander to the orbiter for later relay to Earth. Data relay from the mother flyby spacecraft likely would be possible, but the rapidly changing relative locations of the landing site and the orbiter circling Jupiter may limit how much data could be returned and when communication relay is possible. A recent European study for a Europa lander assumed that the mother spacecraft would have just one chance to directly receive data from the lander in a 10 day period. One argument for excluding a seismometer is that this instrument would produce large amounts of data that may be difficult to return directly to Earth. The European study found that the brief relay between lander and orbiter would have enabled the return of seismic data. Magnetometers, on the other hand, produce only small amounts of data that likely could be directly relayed to Earth (assuming the lander would have that ability).

In the highest resolution images obtained by the Galileo Jupiter orbiter, the regions of Europa that appear to be fractured and have possible ocean material on the surface are extremely rugged; these cliffs are approximately 10 stories tall. Credit: NASA/JPL.

A major challenge for any Europa lander will be that the scientifically most interesting places to study also appear to have extremely rugged terrain which makes landing risky. Berger’s article briefly mentions that the lander would use an autonomous landing system to examine the terrain below it to pick out safe spots to put down. Technologies to allow a lander to image its landing site during descent have been studied for years and were implemented on the Chinese Chang’e 3 lunar lander and are under consideration for NASA’s 2020 Mars rover. During final descent, these systems use images taken by the lander in real time to analyze the terrain below to identify safe landing zones. With an autonomous guided descent, scientists can target an area that overall is rugged but has small safe zones.

What I conclude from the clues Berger supplies is that the Europa landing would be much like the Philae comet lander (although with Europa’s higher gravity, the lander will not bounce across the surface after touchdown as Philae did). The lander would have just a few days to conduct its operations and return the data to Earth. On Mars, we have become accustomed to landed missions that last years with plenty of time to carefully consider where to sample and then conduct follow up studies. A Europa lander will be a mad dash to complete the science goals before the batteries die.

By the end of its life, the lander will have returned our first data directly from the surface of an ocean world that may harbor life that arose independently from the life on Earth.

Launch on the Space Launch System (SLS) booster currently being developed by NASA primarily to support human exploration would significantly shorten the flight time to Jupiter. Other presentations list the nominal cost for an Atlas launch at ~$350M and for an SLS launch at ~$500M. Reducing the cost of operations during the flight to Europa could make the SLS option, which is currently required by law, equal to or cheaper than the Atlas option. Credit: NASA/JPL.

Editorial Thoughts: I of course want to see a lander delivered to the surface of Europa, but I have mixed feelings about the inclusion of a lander on NASA’s first dedicated mission to Europa for two reasons. First, as I will explore in more detail in my next post, adding a lander to the existing Europa mission will push its costs up, perhaps to the $3.5B range when including a launch on the SLS. Congress will need to substantially increase the planetary budget to prevent the Europa mission from crowding out the smaller planetary missions that provide balance to the program. While Congress can pass budget laws directing year to year spending, meeting these aggressive goals will require that the President’s Office of Management and Budget (OMB) accepts the new plan and allows NASA to sign the necessary multi-year contracts with its vendors. In the past, OMB has resisted prioritizing the Planetary Science budget to accommodate a Europa mission.

Second, the driving force behind the expanded mission depends on one Congressman and his continued re-election, his political party’s continued control of Congress, and his health. The alternative approach would be to run the exploration as NASA has run the Mars program by spreading costs out over a sequence of missions. This would be in the vein of the proposed “Ocean Worlds” program currently being shopped to NASA and Congress.

I expect that in the next few months that we will learn considerably more about the lander’s design and NASA’s plans on how it will fit into its overall planetary program.