A Reluctant Dance Towards Europa or Why A Credible Europa Mission is Likely to Cost ~$2B

For the last two years, NASA has been the shy partner refusing to get on the dance floor, and Congress has been the aggressive partner insisting on a dance now.  Recently, NASA has said maybe on another night but only if it’s a cheap date.  While NASA says no for now, Congress looks to be willing to slip the band a cool $100M – on top of $150M already paid – to keep the music playing, but (to keep the metaphor going) has not been willing to fully commit itself to paying the bigger bill to rent the dance hall.

The dance, of course, is the continuing attempt by Congress to have NASA commit to a mission to explore Europa, and NASA’s attempts to delay a mission well into the 2020s.  NASA is also seeking ideas for alternatives to the current $2B Europa Clipper concept that would cost no more than $1B but that also would presumably be less capable.

Compared to the budget waltz, the scientific case for a mission to Europa is compellingly simple.  After the Earth, Europa is considered by many scientists to be the most likely location in the solar system as a home to present life.  It has the key ingredients: an outer layer with lots of water (more than in the oceans of Earth) in contact with the rocky core (source of key elements needed to build the molecules essential for life) and energy (from the tidal heating supplied by Jupiter).  And Europa has had a lot of time for life to evolve.  Its oceans should have been present for most of the life of the solar system.  (This distinguishes it from Enceladus where the weaker tidal flexing of Saturn may allow its internal ocean to freeze for long periods of time.)  The recent observation of possible plumes spewing water into space where Europa’s ocean could be easily sampled has just raised the desire for a dedicated Europa mission.

The Europa Clipper would replace a short-lived Europa orbiter concept with a spacecraft that would fly past the moon several dozen times with a highly capable instrument payload.  At each encounter, the instruments would do low- to medium-resolution studies before and after closest encounter, but would do high resolution studies during the brief period when the spacecraft is less than 1000 km from the surface .  Credit: NASA/JPL.

The Science Goals

In the 1990s and early 2000s, the Galileo orbiter made eleven of flybys past Europa.  That mission all but proved the existence of a liquid ocean beneath the moon’s icy shell and globally mapped the surface features and composition.  Galileo, however, had a crippled main antenna that reduced the returned data to a tiny trickle of what had been planned, so medium and high resolution mapping of the moon covers only small areas.  The spacecraft’s vintage 1970’s technology instruments also lacked the sophistication to identify important substances in the icy surface.  It also did not carry instruments that could probe the structure of the icy shell to look for lakes within the shell or study the shell’s interface with the ocean. 

The standard progression for exploring a world is first flyby it (which Galileo did), then orbit it for globally studies, and then land on it for intensive studies in a single location.  Unfortunately, Europa sits well within Jupiter’s harsh radiation belts, and any affordable orbiter would have weeks to a handful of months to complete its studies and would carry a minimal instrument compliment.

JPL’s engineers and scientists have developed an alternative strategy for the proposed Europa Clipper mission: Fly a highly capable spacecraft that orbits Jupiter, but that toe dips into the radiation belt and conducts its science during several dozen flybys.  The radiation challenges are still significant, but the science that would have carried a cost of >$4B as an orbiter can now be done for ~$2B.

The several dozen flybys is key to the Europa Clipper’s ability to replace an orbiter mission with a multiple-flyby mission.

During the few minutes around closest encounter, high resolution studies are done only for a narrow swath along the ground track immediately below the spacecraft's flight.  Credit: NASA/JPL.



Over several dozen flybys, the high resolution measurements build up into regional studies.  Credit: NASA/JPL.

The combination of low, medium, and high resolution measurements add up to an understanding of Europa as a world over several dozen orbits.  (Acronyms: 13F7 - name for a specific concept for a set of flybys; COT-4 - name for the final campaign (of four) for the Europa Clipper mission; SWIRS - Short-wave infrared spectrometer that would map the composition of the surface.)  Credit: NASA/JPL.

I’ll focus on just one set of requirements and how they link to several key investigations.  To ensure that proposed mission achieves global coverage, the science team has divided Europa’s map into 14 panels.  The science goals require that the spacecraft fly over at least 8 of these panels at altitudes of less than 400 kilometers with a desired goal of 11 panels.  Within each panel, the requirements specify that at least two close flybys occur in each on the Jupiter-facing hemisphere of Jupiter and three on the anti-Jupiter face.  If the minimum 8 panels are evenly distributed between the pro- and anti-Jupiter hemispheres, then 20 flybys are needed to meet the minimum science goals.

This one set of requirements for regional measurements within a panel and a distribution of regional studies across the Europan globe enables several key studies:

“Characterize the ice shell and any subsurface water, including their heterogeneity, ocean properties, and the nature of surface-ice-ocean exchange.

·         “Characterize the distribution of any shallow subsurface water and the structure of the icy shell.

·         “Search for an ice-ocean interface.

·         “Correlate surface features and subsurface structure to investigate processes governing material exchange among the surface, ice shell, and ocean.

·         “Characterize regional and global heat flow variations.

“Understand the habitability of Europa's ocean through composition and chemistry.

·         “Characterize the composition and chemistry of the Europa ocean as expressed on the surface and in the atmosphere

·         “Determine the role of Jupiter's radiation environment in processing materials on Europa

·         “Characterize the chemical and compositional pathways in Europa's ocean.

“Understand the formation of surface features, including sites of recent or current activity, and characterize high science interest localities.”

(Quotes are from the Europa Clipper Science Traceability Matrix.)

The science goals similarly require a number of well distributed flybys to study the interaction of Europa’s ocean with Jupiter’s intense magnetosphere to estimate the depth and salinity of the ocean and to study tides to estimate the ice shell’s thickness. 

The current Europa Clipper mission concept goes well beyond the minimum science goals to deliver on almost all the extended goals that the science community has set.  However, cutting the current mission concept from its 45 Europa flybys to a minimum of 20 or fewer flybys seems unlikely to cut the mission costs in half.  Once you build and fly a spacecraft to Europa that can withstand 20 encounters, operate a suite of instruments, and return a large volume of data between encounters, I suspect that you've already incurred most of $2B cost (but remember that I am neither an engineer nor a planetary scientist). 

Is Cheaper Credible?

NASA managers have formally asked if a credible Europa mission could be done for half the Clipper cost estimate, or around $1B.  This is a good news/bad news scenario.  NASA took the initiative to propose an in-depth study by suggesting spending $15M next year ($85M less than the House of Representatives appears ready to approve for next year, see below).  However, next year’s study would be followed by several years before any mission conceived would actually begin development and a decade or more before it might launch.

NASA issued a Request For Information on concepts for a $1B mission.  It has required that proposers, “meet the majority of the five science goals set forth in the Decadal Survey [priorities set by the scientific community], including the goal to characterize scientifically compelling sites to prepare for a potential future lander mission to Europa.”  Those scientific goals are, in priority order, to:

” Characterize the extent of the ocean and its relation to the deeper interior;

“Characterize the ice shell and any subsurface water, including their heterogeneity, and the nature of surface-ice-ocean exchange;

” Determine global surface compositions and chemistry, especially as related to habitability;

 “Understand the formation of surface features, including sites of recent or current activity, and identify and characterize candidate sites for future in situ exploration;

” Understand Europa’s space environment and interaction with the magnetosphere.

“While characterizing landing sites for future in situ exploration is the fourth scientific priority in the Planetary Decadal Survey, NASA places high programmatic priority on this goal to enable a potential future lander mission to Europa.” (From the Request for Information.)

The request goes on to list the challenges of implementing the mission.  “The primary challenges facing any mission to Europa involve the harsh radiation environment and planetary protection requirements… Planetary Protection requirements for Europa are very strict and involve ensuring that the probability of introducing a viable Earth organism into Europa is [less than one in 10,000].”

The request's details make it clear that proposers must do a solid amount of science and engineering analysis to show that they have a credible concept that could cost less than $1B (not including the launch costs) and make their case in 15 pages

It is common for government agencies to issue these “Requests for Information” to learn whether an idea is credible and worth pursuing.  This request doesn’t commit NASA to any follow up studies, but if its managers judge any of the proposals to be credible, it presumably would follow through with more detailed analyses.

Is a $1B mission idea credible?  I did a thought experiment in a previous post and concluded that technically it likely is.  The Juno spacecraft that will orbit and study Jupiter cost ~$700M.  A mission to fly by Jupiter’s moon Io, deeper in Jupiter’s radiation field, six or so times has been estimated to cost ~$1B.  The European’s JUICE mission will reach Jupiter next decade, flyby Europa twice, and then orbit the moon Ganymede for ~$1.2B.  

If the goal simply is to fly by Europa a few times with a spacecraft with a small number of instruments, then by analogy with these other Jupiter missions, it likely can be done for ~$1B.  The bar, though, for a scientifically credible mission is higher.  A follow-on mission has to substantially enhance our scientific understanding of Europa to justify a cost of $1B to $2B.  Most of the key studies identified by the science team require numerous flybys distributed across the globe.

However, Europe’s JUICE 2020’s JUICE mission to the Europa system is committed to two flyby of Europa with a highly capable spacecraft and instrument suite.  To be justified, a NASA mission must produce significantly better science than the already funded JUICE mission will.  (While the JUICE mission, which is still in design, it has committed to just two flybys of Europa. I suspect that if the engineers conclude it is safe, the mission’s managers will consider one or two additional flybys closer to launch.)

So is there hope for a $1B mission that is scientifically compelling?  Color me skeptical (and several of NASA’s managers are reported to have said they  are skeptical, too), but if there is, I suspect that it will come in one of two forms:

• A proposal suggests a clever way to redefine the science goals in a way that returns the core science with a simpler and cheaper spacecraft.  The team that proposed the Juno mission on its way to Jupiter did this for studies of Jupiter’s deep atmosphere and interior.  The current Europa Clipper multi-flyby proposal redefines the science goals from previous orbiter proposals to substantially cut costs.  Is there another option that can cut costs substantially again?
• A proposal combines limited regional studies with flights through the possible plumes of Europa to directly measure water, and possibly life, expelled either from a lake within the shell or directly from the ocean.  (However, remember that only one of several studies saw data that suggested plumes were present and those measurements were near the limit of detection.  The plumes may be ephemeral or not even exist.  Justifying a mission on the current plume data seems risky to me; a better strategy would seem to be to have a viable mission without the plumes but carry the already planned instruments that would also be useful to study the plumes.  The JUICE mission team is already planning this.)

In a few months, we are likely to learn whether NASA received any proposals it considers worthy of further study.  They key, though, will be whether the science community agrees that the mission meets the core requirements for understanding Europa.  If it doesn't, then the community seems likely to recommend waiting until budgets allow the right mission to be flown.  Missions to each outer planet or their moons occur only every couple of decades.  Why do a sub-par job on the next mission to Europa and then have to do it over a decade or two later to get it right?

The Politics

In the introduction to this post, I said that NASA (and the President’s budget office that writes NASA’s budget requests) and Congress disagree on whether a Europa mission should begin now or wait to begin development several years from now.

The root of the disagreement, as in so many relationships, is money.  Jupiter’s harsh, electronics-frying radiation belts, make any mission that does more than a handful of flybys a technically challenging – read expensive – proposition.  More than a decade’s worth of technology development and mission studies has provided the solutions to most of the technical challenges.  JPL’s scientists and engineers have developed a killer proposal for a dedicated multi-flyby Europa Clipper mission.  At ~$2B, this mission would be cheaper than the Curiosity rover mission currently exploring Gale crater on Mars.

Unfortunately, NASA’s budget is oversubscribed.  The only way to fit the Clipper mission into the budget is to either increase NASA’s budget by several hundred million dollars a year for several years (which I would support as a US taxpayer!) or take the funding from other NASA programs. 

We are left with this strange waltz in which Congress, which ultimately sets NASA’s budget, has not increased the overall budget enough to fully fund the Clipper mission, but over the last two years provided $150M for advanced development work.  This year, the House of Representatives is proposing to put another $100M in the pot for next year.  If the Senate continues its previous support, it is likely to substantially match this funding. 

At the other side of the dance floor, the President’s budget managers and NASA’s managers have made it clear that they don’t want to commit to any Europa mission this decade because of the funding constraints.  They also seem reluctant to commit to any $2B-class science mission because the last two large science missions (the James Webb Space Telescope and the Curiosity rover) went well over budget, which caused substantial harm to the overall science program. 

As a result, today NASA is spending $150M because it’s legally required to (Federal budgets in the US are laws) to advance a mission its senior managers don’t want to do, at least for this decade. 

The House of Representatives has released details of its proposed budget for next year.  Where NASA proposed to spend $15M to study $1B mission concepts, the  House is proposing to spend $100M.  Under the House’s bill none of the funding could go towards a $1B mission (which it doesn't see as credible) but only towards the full Europa Clipper mission. 

We will have to wait for several weeks to see what the Senate proposes.  It will be several months before we learn what the two houses of Congress ultimately compromise on for next year.

2015 Budget Micro-management of the Best Kind

The US House of Representatives has just released the details of its draft proposed NASA budget for Fiscal Year 2015 (starting October 1 of this year).  For planetary science it is good news all around.  In fact, it’s great news because the proposed spending bill micro-manages NASA’s budget to bring NASA’s planetary program closer to the plan laid out in the scientific community’s Decadal Report outlining goals for the coming decade. 

While it is easy to become cynical about politics, it is clear that in this case the politicians and their staffs from both parties on the subcommittee that wrote this draft budget are familiar with the details of the planetary program and are following the scientific community’s lead.  Instead of giving unfunded mandates, all the changes they request are accompanied by proposed increases above the President’s budget proposal.

Missions to Europa would be the big winners in the draft budget bill.  Credit: NASA/JPL/Ted Stryk

	President's Budget	House Draft Budget	Change
Planetary Science Research and Analysis	$165.4M	$170	+$4.6
Discovery	$230.8	$266	+$35.2
New Frontiers	$281.5	$286	+$4.5
Mars Exploration	$279.3	$302	+$32.7
Outer Planets	$95.7	$181	+$85.3
Technology	$137.2	$155	+$17.8
Total Budget	$1,280.3	$1,450	+$169.7

Changes to the President’s budget request in the draft House budget bill in millions of dollars.  Courtesy of Casey Drier at the Planetary Society

In this post, I’ll let the House subcommittee speak for itself through key quotes from the proposed budget bill (starting on page 67).  For the larger context of the budget in Washington’s politics, I encourage you to read Casey Drier’s post at the Planetary Society blog.

“NASA’s request for Planetary Science once again represents a substantial decrease below appropriated levels and would have a negative impact on both planned and existing missions. The recommended funding levels [in this bill] attempt to rectify this problem by supporting both the formulation and development of new Planetary Science missions and the extension of all healthy operating missions that continue to generate good scientific output.”

- The budget provides the funds to continue operating all NASA missions that are currently operating.  The President’s proposed budget did not have funds for either the Mars Opportunity rover or the Lunar Reconnaissance Orbiter.  Money is also provided to continue the Cassini mission at Saturn, which was also included in the President’s budget request.

…”$302,000,000 for Mars Exploration, of which not less than $100,000,000 is for a Mars Rover 2020 that meets scientific objectives laid out in the most recent Planetary Science decadal survey.”

 – This is a modest $8M increase over the President’s budget.  The key requirement is that the rover must meet the requirements laid out in the Decadal Survey, which means that that it must be capable of selecting and caching samples for a possible return to Earth for studies in terrestrial laboratories.  This has been NASA’s plan, but the final payload – the ultimate expression of the mission’s goals – hasn’t been announced, and this is the House’s way of ensuring that NASA follows through.

“The recommendation also provides $266,000,000 for Discovery, of which not less than $30,000,000 is for Future Discovery Missions. The Committee notes that NASA allowed a four year gap to develop between the release of the last Discovery Announcement of Opportunity (AO) in fiscal year 2010 and the expected release of the next AO in fiscal year 2014 (a gap which would have been worse were it not for additional resources provided by the Congress). In order to prevent the recurrence of such a gap in the future and to firmly establish the 24 month mission cadence recommended by the Planetary Science decadal survey, NASA shall ensure that the planned 2017 Discovery AO is issued instead during fiscal year 2016.”

- Selecting Discovery missions every two years instead of every five would significantly enhance the number of planetary missions NASA flies.  The bill adds $30M to the Discovery budget to accelerate the rate at which missions are flown.  This will be big news if the Senate follows suite and this is part of the final budget law.

“For Outer Planets, the recommendation provides $181,000,000, of which not less than $100,000,000 is for a Europa Clipper or comparable mission that meets the scientific objectives laid out in the most recent Planetary Science decadal survey and can be launched in 2021. This funding shall support the completion of science definition, the selection of a mission concept, the release of an instrument AO and other necessary pre-formulation and formulation activities for the Europa mission. While NASA has dedicated some fiscal year 2014 Europa funding to studying the possibility of conducting this mission within a $1,000,000,000 cost cap, the Committee has not seen any credible evidence that such a cost cap is feasible and directs NASA not to use further project resources in pursuit of such an unlikely outcome.”

- The House subcommittee that wrote this budget language continues to strongly support a highly capable mission to Europa.  NASA has formally requested proposals for a mission that would cost half as much as the proposed $2B Europa Clipper mission, but that likely would do much less science that specified in the Decadal Survey.  It will be interesting to see if the Senate includes similar language in its version of NASA’s budget.  If this language survives into the final budget, this will be a strong directive to NASA to plan for a highly capable Europa mission.

“For Planetary Science Technology, …$18,000,000 shall be for assessments and development of promising technologies and techniques for the study and characterization of the surface and subsurface of Europa, including such technologies as landers, rovers, penetrators, submersibles, seismometers and sample analyzers.”

- The House subcommittee really likes Europa.  A mission to land on Europa would have to follow the Europa Clipper mission that would scout possible landings sites.  This is an investment in technology for a mission that isn’t likely to fly until the 2030s.

2015 Planetary Science Proposed Budget – Steady as she goes and then big changes

The President’s proposed Fiscal Year 2015 budget details were released this week.  For the next several years, the budget proposes a steady as she goes plan (but with two “what are they thinking?” surprises).  Then as the current missions in development head to the launch pad, the budget suggests major changes that would dramatically remake the mix of missions that would launch in the next decade.

The broad outlines of the proposed NASA budget have been widely reported.  I’ve gone through the proposed budget and found a move to a very different mix of missions that I haven’t seen reported elsewhere.  To start with the big picture, here are the highlights:

Status quo for missions in flight or under development except that the Mars Opportunity rover and the Lunar Reconnaissance Orbiter missions could end on September 30. 

NASA is recommitting to a vigorous Discovery mission program, but its plans for filling out the rest of its mission portfolio leading into the next decade are unknown. 

Selection of future New Frontiers missions is suspended indefinitely. 

While the Administration finally includes some money to consider options for a budget Europa mission, it’s a one shot affair with no mission development expected until the 2020s.

The President’s budget generally proposes little change in NASA’s science programs for the rest of the decade.  A $65M cut is proposed for the Planetary Science program for FY15, which equals the change in the amount proposed for studying a mission to Europa from FY14.  Solid lines are actual spending, dashed lines projected spending.

Before we look at the details, I’ll provide some background information on the budgeting process.

1. The President’s Office of Management and Budget (OMB) annually prepares a budget proposal for the next year.  The proposal contains two sets of numbers: the proposed spending for the next fiscal year (October 1 to September 30) and a notional budget for the following four years (through FY19 in this proposal) that agency managers use to plan multiyear programs.
2. Each house of Congress then passes its own version of the budget, which are reconciled between the two.  The President must sign the congressionally approved budget for it to become law, giving OMB significant negotiating power with Congress.
3. The final signed budget law will expire on September 30, 2015.  NASA’s managers must spend to match the budget (with some wiggle room) for that fiscal year.   However, they cannot start any multi-year program that isn’t also shown in the President’s out year notional budget.

To understand the impact of the budget on future planetary exploration (the focus of this blog), I've learned to look at three sets of numbers: Funding for missions in flight, funding for missions in development, and funding to start development of future missions.

Funding for missions in flight

Proposed funding for missions in flight (or in the case of GRAIL, just completed).  The budget for operating the Cassini mission isn’t reported separately, and the figures shown are approximate.

The President’s budget proposes to fund all missions in flight with two exceptions.  The first key change in this budget from last year is that the new proposal includes full funding for the Cassini orbiter at Saturn through the planned end of its mission (and fuel) in 2017.  This would mean that the final orbits close to the rings and atmosphere will occur.  As recently as last summer, funding for the Cassini mission past 2015 was in doubt.

Other missions are either funded throughout the five year budget projection (the Curiosity rover, for example), until their expected end of life (the MESSENGER Mercury orbiter), or until the end of their originally planned missions when they will be eligible to justify further funding for extended missions (New Horizons).

The other key change to this portion of the budget, however, is the proposal for premature termination of the Opportunity rover and the Lunar Reconnaissance Orbiter mission.  Both missions are producing good science, and the budget document doesn’t explain why funding isn’t proposed.  In addition to the main budget, the President proposed a supplemental budget enhancement that would be funded through new taxes that would fund both of these missions (among many other programs).  This supplement is given no chance of passage by the current Congress.  Continuing these two missions, then, depends on Congress adding funds to support them in next year’s budget (quite possibly taken from elsewhere in NASA’s budget since NASA’s total budget is unlikely to change much under the two year budget compromise worked out last year by the two political parties).

Proposing to not continue funding the popular and still very productive Opportunity rover is one of the two, “I can’t imagine what they were thinking,” lines in the budget.  I hope that Congress will overturn this.  (I also disagree with not continuing the Lunar Reconnaissance orbiter which is still producing good science, but it doesn’t have the popular following of Opportunity.)

Funding for missions in development

The budget would fully fund development of the three approved NASA missions in development.  Funding is proposed to continue evaluating options for a possible Europa mission that may be developed in the 2020s and for future Discovery program missions.  Solid lines are approved missions, dashed line are funding for expected future missions.

The proposed budget would also fully fund the planetary missions that NASA has in development: the OSIRIS-REx asteroid sample return, the InSight Mars geophysical station, and the 2020 Mars rover mission.  Funding is also included for NASA’s contributions to the European Space Agency’s Bepi-Colombo Mercury orbiter, the 2016 ExoMars orbiter and 2018 rover, and the JUICE Jupiter-Ganymede orbiter.

Funding to start development of future missions

By the end of the decade, NASA would be completing development of the Mars 2020 rover and developing new Discovery-program missions.  No new missions in the New Frontiers or Outer Planets programs are foreseen in the budget for the rest of this decade.  Solid lines are actual spending, dashed lines projected spending.

By funding most missions in flight and continuing development of missions already approved, the budget is largely status quo.  The radical changes to NASA’s program would come for the missions that will follow these.

NASA’s mission strategy has been to fly a mixture of mission that fall into different cost classes.  Some scientific priorities require expensive, highly capable spacecraft, such as the 2020 Mars rover in development.  NASA refers to these missions as Flagships that would cost $1.5B to $2.5B.  (More expensive Flagship missions were flown in the past.)  Flagship missions would do the difficult, high priority studies that simply can’t be done more cheaply.   The expectation has been that one or two Flagship missions would be developed per decade, with missions to Europa and Uranus (in that order) having the highest priority. 

NASA has a second mission class for high priority studies that can be done more cheaply ($700M to $1B), known as the New Frontiers program.   In the past, this program was used to develop the New Horizons spacecraft on its way to Pluto, the Juno orbiter en route to study the interior of Jupiter, and the OSIRIS-REx  asteroid sample return mission that is in development.  For the future, the scientific community has prioritized a Venus lander, a Saturn atmospheric probe, a Trojan asteroid tour and rendezvous, a comet surface sample return, and a Lunar South Pole-Aitken Basin sample return for this program.   The expectation had been that New Frontiers missions would be selected every five to seven years.  As recently as last summer, NASA was planning to select the fourth mission in the series in the next year or two. 

Discovery program missions cost approximately $450M and are competitively chosen from proposals submitted by scientific teams to study any solar system body except the sun and Earth.  (NASA has other programs to study those two bodies.)  NASA originally selected Discovery missions every two years, but that has been stretched to every five years recently.

The new budget proposal would radically shift the mixture of mission classes for the future.  The budget for the Discovery program would be ramped up to a level that would again allow selection of missions every two years.  (In a past meeting, Jim Green, head of NASA’s Planetary Science program, has said that a budget of ~$350M would support starting a Discovery mission every two years.)  However, the budget states that after the launch of the OSIRIS-REx mission, the budget for the budget for the New Frontiers program drops to near zero and no money is foreseen up to 2019 to develop future missions.  (It is silent about whether New Frontiers missions might be selected after that.)

The proposed budget also doesn’t foresee any new Flagship missions to be started before 2019 and looks to see if the highest priority future Flagship mission could be descoped to the equivalent of a New Frontiers mission.  The approach proposed in the budget is the second case where I am left scratching my head wondering what the thinking is.   Thanks to generous funding added by Congress in the last two budgets, NASA has extensively studied a ~$2B proposed mission called the Europa Clipper.  For the FY15 budget, NASA proposes to spend $15M (a substantial cut from last year’s $80M inserted into the budget by Congress for Europa mission studies) to assess the potential for a $1B Europa mission.  Testing different cost points to learn what each could provide is a smart management move.  What doesn’t make sense is that the budget proposes to spend $15M next year, and then nothing for a Europa mission until possibly sometime in the 2020s.  The engineers who will study the descoped mission will have moved on to other projects or retired; technologies available today will be obsolete.  So why bother? 

While Congress has strongly supported doing a Europa mission earlier than the 2020s, it can’t force the formal start of development on a new mission.  Congressional budgets expire every September 30^th.  To start development on a new mission, NASA needs both for its budget to show proposed budgets in future years to complete the development and for Congress to appropriate the funds for that development each year.  Under the proposed budget, we would have one more year of studies and then nothing for perhaps another decade. 

This budget proposal presents almost no vision for NASA’s planetary program following the completion of the missions currently in development.  No money would be spent to prepare for a Flagship mission to launch in the 2020s.  The Outer Planets program shrinks to near zero, and the same for the New Frontiers program.  In the proposed budget, the only firm plan for the following decade appears to be a robust program of Discovery missions, but that alone isn’t enough for a robust planetary science program.

Unless the Planetary Science budget suffers a severe cut at the turn of the next decade, funds should be available for a relatively rich program.  By my back of the envelope calculations, continuing the current budget (with inflation adjustments) would support development of the $2B Europa Clipper, a New Frontiers mission, and five Discovery missions in the 2020s.  Alternatively, NASA could fund three New Frontiers-class missions (including perhaps, a budget Europa mission) and five Discovery missions.  However, preparing to fly these missions requires funding in advance of mission selection to have robust programs ready.

My take is that the new budget proposal is an interim document when it comes to preparing for the next decade’s missions.  The President’s budget managers have placed a low priority on planetary science compared to other NASA programs, and the program’s budget has suffered substantial cuts as a result.  This is the first budget proposal in several years that shows essentially flat spending into the future instead of new cuts.  NASA’s managers likely are revamping their expectations for the planetary program given the new budget realities.  We haven’t heard (and NASA may well not know) what mission portfolio it plans to support in the future within that reality.

The proposed FY15 budget is the first in several years that doesn’t propose substantial cuts in future years compared to the previous year’s budget.  Lines for each fiscal year show what spending was expected in that budget for the next five years.

Boundaries for the Next Discovery Mission Selection

In my post a couple of weeks ago on the selection of NASA’s next low cost planetary mission, I said that the conditions NASA imposed on scientists proposing missions would determine much of what kind of missions scientists could impose.

Yesterday, NASA released a preview for the next competition.  There are some important innovations and a major limitation.

NASA will accept proposals to study any solar system body except the sun and the Earth.  Scientists cannot propose missions to study planetary systems around other stars (NASA astrophysics program funds these missions.)

NASA announced that the budget for the spacecraft, instruments, and data analysis (the Principal Investigator (PI) budget) would be $450M (FY15 dollars).   This is a small increase from the last competition’s PI budget of $425M, and by itself would not keep up with inflation. 

Outside of the PI’s budget, NASA will pay for the cost of the mission launch.  For the first time, NASA will pay for the cost of the mission’s operation outside of the PI budget.  In past competitions, missions with long flight times, and hence high operations costs, were at a disadvantage to missions with low operations costs.  This appears to be an effort to equalize operations costs.  Missions that would benefit are any with flight times of several years compared to the weeks or months to reach Venus, the moon, or Mars.  With operations costs not counted against the PI’s budget, the new competition probably keeps up with inflation compared to the previous competition.  (NASA’s announcement does emphasize that the operations costs projected for a mission must be ‘reasonable’.)

The major limitation for this competition is that NASA will not provide a radioisotope power system for this competition.  While recent NASA presentations suggests it has sufficient plutonium-238 fuel to support a Discovery mission, that fuel could not be prepared in time to meet the expect launch date for this competition.  As a result, any mission that cannot use solar power is effectively eliminated.  This would include missions beyond Jupiter, to the permanently shadowed lunar polar craters, or where large solar panels just won’t work like for a mission that would make multiple landings on a comet (see this description of the CHOPPER mission proposed for the last competition).

NASA traditionally offers scientists various technologies at the space agency’s cost that it would like to see tested in space.  For this competition, NASA says it is considering providing a version of the NASA Evolutionary Xenon Thruster (NEXT) ion propulsion engine as well as heat shield technology for missions that would send a probe into planetary atmosphere.  These former would benefit missions that would require large amounts of thrust such as main belt asteroid missions or comet rendezvous missions.  The latter would benefit missions such as Venus atmospheric probes.

NASA also is considering requiring proposals to include carrying its Deep Space Laser Communications (DSLO) package.  This technology was tested on the LADEE mission currently orbiting the moon and showed that lasers could return much larger volumes of data than traditional radio systems.  NASA would now like to try this technology from a spacecraft in deep space.  Missions with low data rates such as Venus atmospheric probes probably would see little benefit from the DSLO system.  Missions with lots of imaging data such as Venus radar mappers or Io multi-flyby missions would make good use of the DSLO system.

One other new requirement is a limitation on how much of the cost of instruments foreign space agencies can contribute.  NASA has had a limitation that foreign governments could not contribute more than one-third the cost of the total mission.  That cap now also applies to the contribution to the cost of the science payload, too.  This appears to be a way of preventing a proposal team from minimizing its PI costs by filling most of the payload with instruments paid for by other governments.  NASA apparently wants US planetary missions to provide opportunities for US scientists to fly their instruments.

All in all, this looks to be a nice opportunity that keeps the Discovery program on track to continue to support innovative missions to a variety of destinations in the solar system.

Key dates (subject to change)

May 2014 – release of draft Announcement of Opportunity with details for proposers

September 2014 – release of final Announcement of Opportunity

December 2014 – proposals due

May 2105 – selection of two to three finalists for further study

October 2016 – selection of winning mission

December 2021 – launch by this date

Mission to a Metallic World: A Discovery Proposal to Fly to the Asteroid Psyche

Imagine flying deep within the asteroid belt to study the most unreachable location in the solar system: the deep core of a terrestrial world.

That will be one asteroid mission that will be proposed for NASA’s upcoming competition to select its next Discovery mission to explore the solar system.

We know nothing about what the geology of metal world would be like.  Could the impact crater look like frozen splats?  Credit: JPL/Corby Waste

Asteroids are found scattered across the solar system like artifacts strewn across an archaeological site.  Just as a delicate gold necklace and simple rough potsherd can speak the different strata of an ancient society, the many types of asteroids speak of the strata of conditions in the earliest eon of the solar system.  Stony bodies, for example, formed closer to the sun while icy bodies formed further away. 

By studying asteroids (and their cousins, the comets), scientists can study the remains of conditions from the earliest solar system. 

Most asteroids are smallish affairs with diameters measured in meters to kilometers or at most a few tens of kilometers and are usually chips knocked from larger protoplanets by impacts from still other asteroids.  In a few cases, though, the original protoplanets remain largely intact.  By studying these worlds with spacecraft, geologists can examine how the terrestrial planets formed.  On the true planets, that early history is long lost because of geologic activity.

Some of the protoplanets have a familiar structure like Vesta with its rocky mantle and metallic core that resembles the structure of the terrestrial planets.  Others are unlike any world we have explored to date.  Massive Ceres is a rock-ice world with a deep mantle of ice and is a member of a family of asteroids that emit water vapor (some are even comet like with full dust and ice vapor trails).  The asteroid Psyche is a metal world that may be the remnant core of protoplanet. 

(When I first began reading about the solar system several decades ago, comets were icy balls with some dust and asteroids were rocky.  Now we know that comets and asteroids are a continuum and many asteroids contain substantial amounts of ice that would have been water when these bodies still retained the heat form their formation.) 

Asteroids have been popular targets for solar system missions.  NASA has flown two asteroid missions and is building a third with a fourth listed as high priority.  Japan’s JAXA space agency has flown one mission, is building a second, and is planning for a third.  American and European scientists have proposed numerous additional missions.  In the last competition for NASA’s low-cost Discovery program (~$425M missions), over a quarter of the 28 missions proposed would have flown to an asteroid or observed them with a space telescope.

In the competition for the next Discovery mission expected to begin this year, we can expect a similar enthusiasm from the scientific community.  A good portion of the proposals will probably be to fly to one or more of the small asteroids whose orbits are near the Earth’s.  Flights to these worlds are relatively easy, making the missions that orbit them and even land budget bargains and low risk.  In addition, collisions, gravitational influences of the true planets (especially Jupiter), and even the pressure of the sun’s light have scattered the smaller asteroids across the solar system. Within easy reach from Earth are bodies representing a plethora of conditions that were found across the early solar system. 

Scientists who want to study protoplanets have to look to the asteroid belt between Mars and Jupiter.   There the Discovery Dawn spacecraft has finished its studies of the rocky protoplanet Vesta and is headed towards the rock-ice dwarf planet Ceres.

While the Dawn mission picked off two of the most exciting protoplanets, there are plenty more.  European scientists in their last mission competition proposed two main belt asteroid missions (neither selected).    They focused on two classes of asteroids.  The first were asteroids that have been observed to eject jets of water vapor.  The second class was actually a single asteroid – the metal world Psyche.

Scientists planning to propose Discovery missions usually are reluctant to say much about their ideas.  The competition is tough and missions usually are proposed several times.  Why say something that would give a competing team a good idea?  So of the eight asteroid Discovery missions proposed last time, we know very little about what was actually proposed.

Even with the stiff competition, though, some scientists try to build support for their proposals by making some disclosures in public.  It can’t hurt to have the members of the review panels already excited by a mission before they evaluate the proposal.  In general, we hear more about how scientifically interesting a destination is (those facts are widely known) and less about the spacecraft and instruments (what I know many of the readers of this blog are most interested in).  The few times we hear about detailed implementation, it generally is to a destination that seems beyond the reach of a Discovery-class mission where building technical credibility before the review likely helps.  All three of the teams that have proposed missions to the Saturn system, for example, have revealed a fair amount about the implementation.

The team preparing to propose a mission to the metal world Psyche has been relatively open about their proposal although they talk more about the destination than their spacecraft and instruments.

The asteroid Psyche is one of the larger asteroids.  Credit: Lindy T. Elkins-Tanton

Fortunately, the destination is worth learning about.  Stop for a second and ask yourself – what location for all the planets do we know least about?

It’s the cores of the planets.  We can infer much about the size of the cores from seismic data (so far available only for the Earth and the moon but soon also for Mars), gravitational studies that reveal the mass of the core, and measurements of the magnetic field when present.  No one, though, has ever seen a planetary core or directly measured its composition.

The asteroid Psyche may give us that opportunity.  As bodies coalesced in the early solar system, initially random chance brought dust and ice to clump together.  Once a body reach a kilometer or more in diameter (what is called a planetesimal), its gravity became strong enough to pull more material in to it.  At a critical size, the heat from radioactive elements, collisions, and gravitational pressure melted the interiors of these worlds and they became protoplanets. Iron and nickel metals sank to the cores, mantles formed from the lighter silicate materials or ices, and a crust may have formed of either unmelted primitive materials, or by volcanism from the interior flooding the surface. 

Three possible origins have been suggested for the metallic asteroid Psyche (~250 km diameter), all of them intriguing.

Psyche could be an asteroid in which repeated collisions chipped off the crust and mantle, leaving the core a naked body.  If this is the case, then a mission to this world would be the equivalent to a mission deep below the surface of any of the terrestrial planets to examine their cores.  It’s a journey that is possible only because chance created and then preserved from ultimate destruction by further collisions Psyche’s naked core. 

Psyche could be the remnant of the collision of two protoplanets that shattered and expelled the core of the smaller body to become Psyche.  In this case, we wouldn’t get to examine an intact protoplanet’s core.  We’d still get to examine the composition of a protoplanet’s core, though, and also see how a world composed almost purely of metal formed itself following a collision.  Collisions such as this would be been common in the early solar system.  One is believed to have created the Earth-moon system. All planetary cores, in fact, almost certainly formed from multiple generations of fragmentation, differentiation, and merging of previous cores.

And finally, Psyche could have formed so close to the early sun that all materials other than metals (and some silicates) would have been evaporated and have been unavailable for planet building.  Later migrations of Jupiter and Saturn in and out of the inner solar system could have moved this world to its present location in the asteroid belt.  In this case, a mission to Psyche would show us an entirely new class of world.

Telescopic observations reveal that Psyche’s surface is 90% metallic and 10% silicate rock.  A spacecraft orbiting Psyche likely could distinguish between these scenarios by measuring the composition in detail and looking at the arrangement of the silicate material.  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.

Here are some of the key questions a spacecraft would explore at Psyche:  How did this large metal world form?  If it is a remnant core, what is the composition and structure of a terrestrial world’s core?  If Psyche was once molten, did it solidify from the inside out, or the outside in?  We have a number of meteorites from a single metallic asteroid (the group IVA iron meteorites); is Psyche their source?  The metallic asteroids appear to be much less dense than the metallic meteorites; are these asteroids rubble piles? 

We know a great deal about the geology and surface features of rocky worlds, icy worlds, and will learn about rock-ice worlds when the Dawn spacecraft reaches Ceres next year. Metal worlds may differ significantly in their appearance. What does the surface of a metal world look like?  Imagine how strange a crater might appear. Laboratory tests of craters in metal show that sometimes the ejecta flaps freeze before they fall; could this happen on a planetesimal?

Like the Dawn spacecraft, the Psyche spacecraft would use solar electric propulsion.  As for instruments, the proposal team’s Principal Investigator, Dr. Lindy T. Elkins-Tanton of the Carnegie Institution for Science,  told me, “We hope to learn not just about the surface of this metal body, but also about its interior, which requires geophysics. We'll be carrying a magnetometer, and we'll use the spacecraft itself to develop a detailed model of the body's gravity field. With these measurements and knowledge of topography, we'll get information on internal structure.

“We'll have an imager, of course, in the hopes of seeing some unforeseen new metal geology, and to count craters to measure the age of the surface, among other goals. Measuring the surface compositions of a metal object remotely is more difficult. Infrared spectrometers are great for silicates, but only gamma ray spectrometers can measure metal composition. We expect, though, to see some silicate materials along with the metals.”

I asked Dr. Elkins-Tanton about the possibility of flying to a second asteroid.  She told me that they looked at this and concluded that it wasn’t feasible.  No other asteroid visit would address their questions about metallic asteroids (and the instrument suite that would be wanted for a comet-like asteroid, for example, would be different).  It also would be difficult to fit second asteroid visit into a Discovery mission budget.

In my previous post, I wrote that Discovery mission competitions surprise and delight us with the cleverness of the missions proposed.  While we will hear little about many of the missions likely to be proposed for the asteroids, the Psyche mission gives an idea of what is possible.

You can read a two page summary of the science goals for the Psyche mission at this link.

My thanks to Dr. Lindy Elkins-Tanton for reading a draft of this post and making several useful suggestions.