Countdown to the Next NASA Discovery Mission Selection

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

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.

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Selecting the Next New Frontiers Mission

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.