Decadal Survey: The Candy Store Posted

As part of its analysis, the Decadal Survey commissioned 25 mission studies to define potential missions it would select its final list from.  The full list of mission studies, plus three technology studies to enable missions in the 2020s and beyond, have been posted (http://sites.nationalacademies.org/SSB/SSB_059331).  As one poster at Unmanned Spaceflight put it, this is a candy store for those interested in future planetary missions.

In future entries, I'll be summarizing the reports (a typical length is around 30 pages) and where appropriate comparing them to each other and to past missions and other mission concepts.  Generally, each report will get its own entry, but in the case of similar mission types, I'll compare the mission concepts in a single entry.  I'll also combine the summaries with my continued list of the five missions that I find most compelling for the coming decade.

To kick off the process, I'll post a table comparing the missions for cost and mission flight times (be sure to read the notes on the table for important caveats).  In going through this list, I was happy to see that a large number of missions are reasonably close to the fully burdened New Frontiers mission cost of ~$1,350M inflated at 3% per year for Fiscal Year 2015 costs.  Another group of missions could probably fly at a New Frontiers mission and a half budget.  Assuming that the Max-C rover, the Mars Trace Gas Orbiter, and three Discovery missions fly in the next decade, this would allow two to four of the sub-$2B missions on this list to fly.

Click on the list for a larger version.

Notes on the table:

• A number of the reports analyze several options for a mission target.  In this case, I picked either the lowest cost or a typical cost and did the same with the mission timeline.
• The mission dates can be somewhat arbitrary.  For many missions, launch windows occur every year to every few years.  For the purposes of the studies, a given time frame was chosen.  Use the dates to get a feeling for how long the flight to the target would take and how long science would be gathered at the target.  For missions that would involve multiple targets or that require entry into orbit around Jupiter or Saturn, the arrival date is the date at the first target or orbit insertion around the major planet.
• The cost estimates were prepared by the mission assessment teams.  These are not the rigorous cost estimates that will be prepared by an independent team for a subset of  these missions that the Survey considered most likely to be recommended.  The costs, therefore, should be considered approximations.  A difference of a couple of hundred million dollars may not be significant, while a difference of a billion dollars almost certainly is.  In addition, early cost estimates are often low, and many of these estimates may also be low.  Where the various mission options came with widely different costs, I showed the range of estimates.

The next blog entry will describe the two mission concepts that together would be for me be the third most compelling mission for the coming decade.

Decadal Survey Endgame

A single presentation slide has been posted on the planetary Decadal Survey webpage listing the schedule towards the public release of the recommendations (next spring) and final document (next August).  (Slide reproduced below.)  The draft report and recommendations should now be with reviewers.  The Surveys traditionally have run a tight review process with no leaks, so the public will have to wait six months to learn what the next decade's program will look like (assuming budgets come through and no major cost overruns).

However, it's fun to speculate what the recommendations might look like.  With that in mind, I'll publish my best guess on what the Survey might recommend.

The last planetary Decadal Survey had four themes to guide mission selection.  I have not seen anything that I predict will replace these priorities althought they are likely to be updated: 1. The First Billion Years of Solar System History; 2. Volatiles and Organics: The Stuff of Life; 3. The Origin and Evolution of Habitable Worlds; 4. Processes: How Planetary Systems Work.

Two key missions from the last Survey have yet to receive formal approval: an Europa orbiter and Mars sample return.  Both remain highly relevant to the priorities listed above.  Both I think are likely to be recommended in the next Survey.  (Both are also expensive, so this is the prediction that I have the least confidence in.)  Titan and Enceladus have increased in importance, but technology is not yet ripe for a multi-billion dollar Flagship mission to these targets.  I predict that the Survey will recommend a lower cost missions to these moons as a gap filler in the next decade.  Scientist-led Discovery and New Frontiers missions also are likely to remain a priority to balance out the program with missions to additonal targets.

Based on these assumptions (and some will be proved wrong), here is a program that would address them and that would fit within the current budget adjusted for inflation over a full decade (costs are either based on publically published numbers or are swags (MTGO and Titan/Enceladus):

Some notes on this possible program:

The Mars missions would provide a head start on a Mars sample return.  However, I would not start the subsequent elements of the return until a cache is ready on the surface of Mars with samples known to be high priority

If budgets prove tight, I would cut the Jupiter Europa Orbiter back to ~$2B to focus only on the most urgent measurements (and sacrifice a good portion of the Jupiter system science).  A Discovery mission might also be cut.

In this thought experiment, the Titan/Enceladus mission would a PI-led mission that would substitute for a second New Frontiers mission in the decade.  The suggested budget would cover the cost of a New Frontiers-class orbiter and a Discovery-class in-situ element such as a lake lander or a plane.  What might be actually proposed by the winning PI might be quite different.

The 2011 New Frontiers mission would be selected from the three missions currently in competition: a Venus lander, a near Earth asteroid sample return, or a lunar sample return.

I have been impressed with the creativity of the Discovery mission proposals and suggest four missions in the coming decade.  Now that NASA no longer requires the launcher to be paid out of the PI budget, capable missions should be able to be flown.  The PI for the proposed Io Volcano Observer, for example, has said that the previous budget limits didn't quite work, but that the new budget limits would fully fund this mission.  (The budget suggested, though, is based on NASA's full cost, which includes launchers and other items.)

There are many losers in terms of exciting and important missions that wouldn't be included in this guess at what the Survey might recommend.  The two that I personally would most regret not seeing would be the proposed Argo Neptune-Triton-KBO mission and a Mars network mission.

When the Survey publishes its recommendations, I'll come back and score my predictions.  I hope I do better here than I have done picking stocks :>

Thoughts on Astronomy Decadal Survey

The past few days, I've read through the Astronomy and Astrophysics Decadal Survey report released last week.  If you are interested in these fields, I encourage you to look through the report.  While it is long (225 pages), the 17 page executive summary and 32 page overview of the state of the field are worth reading.  You can download the complete report. or read good summaries of the recommendations at the journal Nature or at Spaceflightnow.

The recommendations of the Survey have been widely reported, and I won't rehash them here.  Instead, I'll look at the report for clues as to how the Planetary Decadal Survey may approach its recommendations.  Before doing that, there are three key differences in the astronomy and planetary programs that must be acknowledged.  First, the astronomy Survey covers both space missions and ground facilities.  The planetary Survey also can prioritize ground facilities, but in general, the trend is has been to ensure funding for access to facilities already built.  Second, the NASA astronomy program is expected to continue to spend the bulk of its funds on the James Webb Space Telescope through the middle of this decade.  As a result, the proposed space portion of the astronomy program appears modest with just a single major mission firmly recommended.  And third, the incremental cost of meaningfully increasing our knowledge in planetary exploration appears to be greater than in astronomy.  The report notes that the three highly successful Explorer astronomy missions of the past decade together cost $560M.  The budget for a single mission in the equivalent planetary program, the Discovery missions, is $425M.  (Astronomy missions can be expensive, though.  Two ground based telescopes recommended by the Survey would cost $465M and ~$1.1-1.4B and two lower priority space missions would cost several billion dollars.)

The astronomy recommendations are based on conservative budget assumptions that assume flat spending for the NASA portion of the budget.  It has been common in reports of this nature to request budget increases.  With this report, the optimistic scenario is that NASA astronomy and astrophysics budgets will increase for inflation and the pessimistic scenario is that they won't.

The astronomy recommendations are built around two recent key advances in our understanding of the universe: the discovery that dark energy is the major constituent of the universe and the rapidly expanding family of known extra solar planets.  These two areas have radically changed our perceptions of the universe and how solar systems form.  I don't believe that there has been equivalent discoveries in the planetary program in the past decade.  We have much stronger evidence that Mars likely preserves its ancient history and possible record of life and that water was and is abundant, but those discoveries could be viewed as expected.  We have also learned that Titan is a more fascinating world than expected and the geysers of Enceladus were truly unexpected.  These discoveries argue for continuing heavy funding for Mars exploration and perhaps shifting missions from the ice-ocean moons of Jupiter to the ice-ocean moons of Saturn rather than switching, for example, from a Mars focus to a Venus focus.  (If you disagree, please leave a comment!)

The astronomy Decadal Survey chose to make its highest recommendations for general purpose instruments -- as space borne Wide Field Infrared Survey Telescope (WFIRST) and an Earth-based Large Synoptic Survey Telescope -- that can address both the two focus topics and a variety of other questions.  In the planetary field, the trend is to more specialized missions that investigate one body in depth (e.g., a single comet) or a particular topic (trace gases at Mars or the lunar gravity field).  Proposed missions to explore wide ranging phenomena that include geology, atmospheric sciences, and fields and particles have become relatively rare and expensive.  Two examples of proposed missions that would be wide ranging are the Jupiter Europa Orbiter that would explore the entire Jovian system and the Venus Flagship mission that would explore the surface and atmosphere of Venus both remotely and in situ.  Both missions have price tags greater than $3B compared to the $1.6B WFIRST.

The astronomy Survey made clear choices between fields.  Survey instruments received preference over higher resolution instruments.  Infrared astronomy received preference over high energy (X-ray and gamma ray) astronomy missions that were ranked lower and would fly only if US funding permits and international cooperation occurs.  I believe that we are likely to see similar clear preferences from the planetary Survey.  Fiscal credibility will, I believe, be a major criteria for the planetary Decadal Survey.  Steven Squyres, head of the Survey, as warned of sticker shock, which could result in only one no large (>$2-3B) missions being recommended.  (See Sticker Shock and Decadal Survey Showdown.)

The astronomy Survey made as its second priority for space missions an expansion of the small PI-led Explorer program, with a request for funding increases from $40M per year to $100M per year starting in 2015.  Similarly expanding the planetary PI-led New Frontiers (~$650M each) and Discovery (~$450M each) missions from 2 and 3 per decade, respectively, likely would require a decision to forgo either the Jupiter Europa Orbiter or the Mars sample caching rover.

The astronomy Survey made international cooperation a key element of several of its recommendations.  WFIRST could be combined with a less ambitious ESA mission with similar goals.  The third and fourth priority space missions apparently would fly only with substantial ESA contributions and, in the case of one mission, Japanese contributions.  On the planetary side, NASA already is collaborating with ESA on 2016 and 2018 Mars missions and discussing collaboration with ESA to explore the Jovian system.  (All three ESA large class missions in competition for selection involve collaboration with NASA.  One is the Jupiter Ganymede Orbiter and the other two are the astronomy Survey's third and fourth space mission priorities.)  The planetary Survey may also prioritize missions that require substantial international collaboration.  Beyond the missions already in discussion, the planetary survey might, for example, prioritize a small scale orbiter to continue studies of Enceladus and Titan while also suggesting carrying along one or more foreign probes for in situ exploration of Titan.

The astronomy Survey prioritized development of technologies for key missions desired for the decade (2020s) following this coming decade.  The planetary Survey is considering similar recommendations.  Technologies that have been discussed for development in this coming decade to prepare for the next include Mars sample return, technologies for Titan exploration, and cryogenic sample return from a comet.  At the same time, the planetary Survey will have to decide whether or not to make use of key technologies developed in the past decade to allow an Europa orbiter and develop and operate rovers on Mars.  A recommendation not to use those investments may mean that the expertise may be lost if the supporting engineering teams are disbanded for the lack of an immediate flight opportunity.

To sum up, I would expect the planetary Survey to select clear winners and losers among the big ticket missions in response to a tight budget forecast, recommend a continued (and possibly expanded) program of small missions, strongly urge international cooperation, and recommend technologies for development to enable key missions to fly in the 2020's.

Latest Decadal Survey Update

The following open letter from the Survey's chair, Steve Squyres, was published today.  You can read the original at http://sites.nationalacademies.org/SSB/CurrentProjects/ssb_052412#letters.

Dear Colleague:

This is the sixth newsletter to the community regarding SolarSystem2012, the planetary science decadal survey. The key points in this newsletter are these:

1. The five decadal survey panels have completed their integration of the inputs from the community, and have provided their recommendations to the steering committee.
2. Cost and technical evaluations for the highest priority missions recommended by the panels are nearing completion.
3. Final prioritization of mission candidates and other activities by the steering committee is underway, and will be completed within the next few weeks.
4. A report is being drafted, and we expect it to begin a comprehensive peer review process beginning in late September.
5. We hope to have a final report ready to present to the community by next spring.
6. More information is available on the SolarSystem2012 web site: http://sites.nationalacademies.org/SSB/CurrentProjects/ssb_052412

Late spring and early summer were an exceptionally busy time for the five panels, as they finished working through all of the inputs from the community, integrating them for inclusion in the final decadal survey report. The statistics on the community inputs were impressive, with 199 white papers written by 1691 unique authors and co-authors. The panels also worked closely over this period with the Applied Physics Laboratory, Goddard Space Flight Center, and the Jet Propulsion Laboratory to perform detailed studies of a large number of candidate missions that arose from the community inputs.

After receiving the mission studies from the panels, Aerospace Corporation, under contract to the NRC, has performed a number of detailed cost and technical evaluations of the candidate missions. Most of these evaluations are now done, and the final few will be completed within the next two weeks.

Once the steering committee has received all of the scientific inputs from the panels and all of the technical and cost evaluations from Aerospace, the final prioritization of mission candidates will take place. The challenge, of course, is finding the best solar system exploration program that fits the projected budget.  Much of the prioritization has already been done by the panels themselves, so the number of decisions that the steering group will have to make is small. As always, our decisions will be driven by our assessment of the community’s views on the science value and cost effectiveness of all the missions and other activities under consideration. The final prioritization will be completed within the next few weeks.

A report summarizing the current state of knowledge in planetary science, the key outstanding science questions, and the affordable mission candidates and other science activities that best address those questions is being drafted. Most of the report is now written, and we expect to have a final draft done within the next two months. Once that draft has been submitted to the NRC, it will undergo a long and rigorous peer review process, per NRC standards. Many of you in the community will be asked to review it; if you do get asked to provide a review, a timely response will be greatly appreciated!

As soon as the report has been through the review and revision process, it will be released publicly. We expect that the release date will be sometime in the early spring of 2011. After the report has been released, we will also be able to provide briefings about it to the community at major science conferences… so stay tuned for those.

I’d again like to thank everyone in the community for your many inputs to this process. The set of activities that we have studied is breathtaking in its scope, and finding the subset that best addresses your highest priorities while fitting into a limited budget is turning out to be both challenging and rewarding. I’m excited
about the recommended plan that is emerging, and I think you will be too.

As always, more details, including archived webcasts of meetings, agendas for past and future meetings, and materials presented to the Steering Group and panels, are available at the SolarSystem2012 web site: http://sites.nationalacademies.org/SSB/CurrentProjects/ssb_052412

Best wishes,
Steve Squyres
SolarSystem2012 Chair

Editorial Thoughts: The Survey is in the publicly quiet time where priorities are being set and justified.  We are unlikely to hear much about the missions selected until the release of the report next spring.

I suspect that the prioritization by the steering committee may not be as easy as suggested by this letter.  There are at least two or three Richter scale decisions: Should any of the flagship-scale missions (Mars sample return caching rover, MAX-C, Jupiter Europa Orbiter, Saturn-Titan-Enceladus orbiter) that likely will top at least some of the panel's priorities be funded and if so, how many?  Should substantial funds be committed to development of follow on elements of the Mars sample return to allow the fastest possible return of samples cached by MAX-C?  Should one or two destinations (or types of destinations, e.g., comets) be prioritized and receive substantial funding much like Mars was in the last decade?

The easiest solution would be to pick the top missions from each panel (Mars: likely Trace Gas Orbiter and ExoMars/MAX-C, Outer Planets: likely Jupiter Europa Orbiter, etc.) and fund them until the likely money is gone.  However, if any of the flagship-scale missions that may be the highest priority of a panel run into serious cost overruns, then paying for the cheaper lower cost missions may not be possible.  This happened with both the last astronomy (James Webb Space Telescope) and planetary (Mars Science Laboratory) surveys.  The technical and cost evaluations being done will help avoid this problem, but probably not eliminate the risk.

A recent report by the National Research Council showed that many missions experience their major overruns well into development when the designs are presumably well understood.  From the report:

• "Past studies of cost growth in NASA Earth and space science missions calculated values for average cost growth ranging from 23 percent to 77 percent.
• "Relatively little cost growth occurs between preliminary design review (PDR) and critical design review (CDR). 
• "A majority of cost growth occurs after CDR, with the rest occurring prior to PDR.For one large set of 40 missions, 80 percent of the total cost growth (in absolute dollar terms) was caused by only 11 missions."

And, "So 75 percent of cost growth occurs after CDR. Primary Reference 5 also analyzed the evolution of cost growth over time and concluded that “it is important to notice that, unlike the mass and power growth time trends, cost growth is typically not recognized until after CDR."  (PDR is the preliminary design review that occurs early in the project while the CDR is the critical design review that occurs later before committing to development.)  Cost overruns on larger missions often are more damaging than overruns on small missions (25% of $3B is much more in absolute dollars than 25% of $650M).

At the same time, I personally would not like to see a list of missions that are all safe because the technologies are firmly developed.  If I were to wager a beer, my guess is that the Survey will prioritize only one flagship scale mission and fill out the rest of the program with smaller New Frontier and Discovery class missions.  But I wouldn't bet more than a beer on this prediction.

I look forward to seeing how the Survey balances these conflicting priorities.

Astronomy Decadal Survey

Running in parallel with, but about nine months ahead, of the planetary Decadal Survey has been an astronomy decadal survey.  The results of that survey will be released on August 13.  While the results likely will be widely reported, this is the link to the official site http://sites.nationalacademies.org/BPA/BPA_049810

Unfortunately, you probably will not read about the results first on this blog.  I will be out in the field helping a friend out with some research.  I should have a summary within 2-3 days afterward, however.

This impending announcement got me to revisit the schedule for the planetary Decadal Survey.  It looks like the first time that the public will see the results will be March of next year.  Drafts will begin circulating to reviewers in the fourth quarter of this year, but leaks historically appear to have been rare.  Here is the schedule presented at the Outer Planets Assessment Group (OPAG) last spring:

2010
1st Quarter Panel reports finalized
2-3rd Quarter Prioritization and drafting of survey report
4th Quarter Draft survey report to reviewers, Report revised

2011
1st Quarter Report approved, NASA briefed and report released ( prepublication-format)
3rd Quarter Printed report released

Unfortunately, this means that news for future planetary exploration may be a bit slow for the next several months as everyone waits to hear what the final plan will be.

Sample Return Missions

Artist's conception of the MoonRise lunar return mission that is a finalist for the current New Frontiers selection.

If you look at the list of missions being considered by the Decadal Survey, a few themes stand out.  One is the exploration of the ice and ocean moons of Jupiter and Saturn (Europa, Ganymede, Titan, and Enceladus), another is the exploration of Venus, and a third are sample return missions.  (A sprinkling of individual missions to other worlds such as Mercury, Chiron, and Neptune-Triton round out the list.)  [Tidbit: One recent article listed the number of missions being considered  by the Survey as 28, up from the list of 25 posted on its website.  The potential missions to select from may be even more interesting than the current list -- which is already quite an interesting list.]

A number of my blog entries have summarized ideas for all of these themes, but I have given more space to discussing campaigns of missions to ice-ocean moons and Venus than I have a campaign of sample return missions.  This blog entry will try to provide balance by considering sample return missions.

The return of samples from solar system bodies has been a focus on planetary mission planning for decades.  While the instruments carried by spacecraft are marvels of engineering, they must be built to meet severe constraints for mass, size, and power.  Many of the instruments routinely used on Earth exceed the size and mass of the entire spacecraft; in the case of the synchrotrons used to study the Stardust comet grains, the instruments exceeded the size of the launch pad used for the mission.  The instruments in laboratories can probe individual grains in exquisite detail and compositional resolution that no spacecraft can.  Unlocking many of the secrets of the solar system and its worlds will require bringing back samples to Earth.

Unfortunately, sample return missions are inherently costly.  As with a non-sample return mission, a spacecraft must be delivered to its target world.  Most mission concepts include a fairly robust suite of instruments to survey the target body and to select optimal sampling sites.  (The MoonRise lunar sample return mission is an exception; the fleet of recent missions to the moon already have provided the remote sensing context.)  Just to get there and survey the locale requires a fairly capable mission. Then the sample must be collected, which can require complex sample acquisition, handling, and storage devices.  The spacecraft, or a portion of it, must maneuver back to Earth and successfully deploy a return capsule with the sample through the atmosphere.

There are a range of mission complexities and corresponding costs.  At the low end, the Genesis solar wind and the Stardust comet missions were able to capture their samples in flight.  The next step up would be to sample a near Earth asteroid or a comet.  Such missions do not require sophisticated ascent vehicles, but the ultra-low gravity and poorly understood surfaces create their own engineering problems. A sample return from our moon would require a capable lander and ascent vehicle.  And at the far end of the scale would be a Mars sample return mission that would require multiple launches and a small flotilla of craft to gather and return the samples.

Five possible targets for sample return missions are being studied by the Decadal survey: the moon, a near Earth asteroid, a comet, Enceladus, Mars.  The first three targets possibly could be accomplished within the budget of a New Frontiers mission (~$650M).  Comet sampling missions could range across a wide range of prices from mission that collects dust during repeated low-speed passes above the nucleus (Discovery class?), to a mission that returns a warm sample with volatiles in liquid form (New Frontiers?), to a mission that returns frozen volatiles (perhaps 2X New Frontiers cost?).  At the high end of the missions would be a Mars sample return mission at a possible cost of $6-7B.  (I have yet to see a cost estimate for an Enceladus sample return that would collect ice particles while passing through that moon's geysers.)

The Decadal Survey could decide that further missions to flyby, orbit, and land on these worlds for remote sensing and in-situ studies are unlikely to provide more than incremental increases in our knowledge of these worlds.  By the time a sample return mission could be flown to each target, we will have orbited or rendezvoused with three asteroids and flown by several more, have rendezvoused with and landed on a comet and flown by several more, have studied the moon in depth from orbit and sampled the near side, and will have orbited and landed on Mars many times.  A revolutionary increase in our knowledge may require bringing home samples.

What might a sample-return focused set of missions look like?  At 2011 spending levels (adjusted for inflation), NASA will have ~$13B to spend on planetary missions in the coming decade.  Here is a possible breakdown of missions and possible costs (costs are best guesses from estimates published in various sources; many are probably wrong):


Near Earth asteroid sample return      $1.2B*
Warm comet sample return                $1.2B*
Lunar sample return                           $1.2B*
Mars Trace Gas Orbiter**                   $0.5B
Mars sample cache rover                    $2.5B
Technology development for
   subsequent Mars sample return
   elements                                         $1.5B***
                                                        $8.2B from a projected decade budget of ~$13B

*Assuming the mission could be done for the fully burdened cost of a New Frontiers mission
**Needed to image landing sites and serve as data relay for the Mars sample return missions; cost is a guess and probably doesn't reflect NASA's planned costs
****A guess and possibly low


Editorial thoughts: A program focused on ice-ocean moons, Mars, or sample returns would be intellectually sound.  Where the Decadal Survey ultimately decides to place its focus will  be known in a few months.  I've discussed this with a few members of the planetary science community.  In many respects, the mission mix reflects which scientific specialties receive favor.  Missions to ice-ocean moons, for example, favor scientists with expertise in remote sensing and in-situ instruments.  Sample return missions favor scientists with expertise in laboratory analysis and laboratories with the right instruments.  The Survey may ultimately decide on a program that is a mixture of elements to serve the needs of all groups.

Long term readers of this blog know that I am skeptical that a Mars sample return mission will every fly.  That's not because I don't believe that a sample return would return scientific knowledge equal to the price tag.  Rather, I doubt that the political systems of space faring nations will foot the cost short of a previous mission finding clear signs of possible life, past or present.  (Note to my Congressman and Senators: Feel free to prove me wrong.)

Whatever goals the Decadal Survey sets for NASA, the Japanese space agency is planning a second near Earth asteroid mission and the Russian space agency is planning a sample return from the Martian moon Phobos.  The ESA is planning to issue a call for another round of proposals for medium sized science missions, and a near Earth asteroid mission is likely to be proposed again.  Two of the finalists for the current NASA New Frontiers mission are sample returns (from the moon and a near Earth asteroid).  It would seem that sample return missions will be playing an increasingly large role in programs of planetary exploration.

Decadal Survey Showdown

Last week, the journal Nature published an update on the challenges facing the Decadal Survey.  In a nutshell, the planetary program has three major programs it would like to fund, but money for only two.  The article focuses on the contention between two of those programs, a three part $6-7B Mars sample return and a $3.2B Jupiter Europa Orbiter, and concludes that it's unlikely both could fit into the probable budget for the coming decade.  However, if that budget turns out to be close to $12B (which would be the approximate budget presuming similar funding to this year carried forward for a decade), then both missions could be funded.  Doing so, however, would squeeze out the third program of smaller Discovery (~$800M) and New Frontiers (~$1.2B) missions that provide balance and breadth to the program.

"As usual, says committee member Stephen Mackwell, director of the Lunar and Planetary Institute in Houston, Texas, there is too little money for too many ideas. 'We have to deal with a whole Solar System of possibilities,' he says.... 'I find it very hard to see doing them both in the decade,' says Fran Bagenal, former chairwoman of an external NASA planetary-science advisory committee... What's more, attempting a Europa mission and the Mars sample return at the same time could crowd out smaller missions to other parts of the Solar System, says Alfred McEwen, principal investigator for the HiRISE camera on the Mars Reconnaissance Orbiter, which is currently imaging Mars... "What Squyres has called 'sticker shock' for the biggest missions could bias the survey in favour of small- and medium-cost mission lines known as Discovery and New Frontiers. 'I could put together a spectacular programme without either one of those [flagship missions]. There are many ways to slice this,' says Squyres."

Editorial Thoughts: This crunch between desires and budgets isn't a surprise.  In my analysis of NASA's budget for the last two years, I have not seen a way to fund all three programs within the probable budget for the coming decade.  The increasing political focus on cutting federal budgets would seem to make it unlikely that the planetary program budgets will grow, and we may well see cuts.  The Nature article points out that the proposed Precursor missions could add additional missions to the line up.  However, the budget for these missions seems extremely uncertain as the administration and Congress argue over the nature and budget for the manned spaceflight program that would pay for the Precursor missions.  If any of these missions survive, I suspect that the focus will be on near Earth asteroids, which would be the first focus of manned exploration.

What follows is my analysis of the pros and cons for a program that focuses on any of the three major program options.

Mars Sample Return

Pro: The analysis of carefully selected samples from Mars would revolutionize our understanding of Mars and, by extension, conditions on the early Earth.  If those samples include signs of past or current life, then the mission will revolutionize our understanding of our place in the universe.  The ability to tease out insights from samples with sophisticated instruments in terrestrial labs cannot be overstated.  While instruments on planetary probes are engineering marvels, mass, volume, and power restrictions restrict their sensitivity.

Con: While Mars sample return missions have been studied for decades, detailed engineering analysis has rarely been done.  The current concept for a three part mission is still fairly new, and the possibility of rapidly rising costs is real.  Then there is the question of whether there is the political will to fund a mission this large.  Political support would have to be sustained through 2-4 presidencies (depending on whether incumbents win re-election) and 8 Congresses.  The complexity of the program with three major mission elements (a sample colleciton rover, a Mars lander with ascent vehicle, and a spacecraft to fetch the samples from Martian orbit and return them to Earth) means that many mission elements must go off without a failure to actually return the samples.  There is also the question of where and how to sample.  We know enough about Mars to pick a good location to sample, but will politicians fund this large a program without assurances that we already know that the chosen sampling location is optimal?  And should samples be taken from near the surface (current plan), from the shallow subsurface (where ExoMars will sample), or from the deep subsurface?

Jupiter Europa Orbiter

Pro: This mission appears technically ready to enter development after a decade of technology development and analysis.  Europa is one of the most likely spots in the solar system in which to find life, and the mission would also study the rest of the Jovian system.  The proposed spacecraft will have the capability to study Europa in depth and to locate places on the surface where ocean material has recently been brought to the surface where future landers could study it.

Con: This mission is a bet that Europa (1) harbors an environment capable of supporting life and that (2) locations can be found near at the surface where future (expensive) landers could explore in more detail.  Without the possibility of explorable life (life locked below a hundred kilometers ice would be unreachable with current technology and budgets), would the planetary community choose to spend $3.2B to explore this moon?  This mission also requires a larger stockpile of Pu-238 to fly than NASA currently has on hand.  Either the Russians would have to agree to resume sales of Pu-238 to the U.S., or the U.S. would have to restart Pu-238 production, which may not occur in time to fly this mission by the end of the decade.

Discovery and New Frontiers Missions

• 2 small flagship ($1.8B or 1.5 times the standard New Frontiers mission) missions that might fund a Mars rover, a network of Mars landers, a cryogenic comet sample return, or a Jovian or Saturn orbiter to continue the exploration of the moons of those worlds.
• 4 standard (~$1.2B) New Frontiers missions that might include a Ganymede orbiter with Europa and Callisto flybys; a near Earth asteroid sample return; and Venus lander; a lunar sample return; a mission to flyby Neptune, Triton, and Kuiper belt object; or a modest Enceladus mission.
• 4 Discovery (~$800M) missions that might fund the U.S. contribution to the Mars Trace Gas Orbiter, remapping Venus with radar at higher resolution, an Io volcano observer, a Titan lake lander, a Trojan asteroid mission, a Venus balloon mission, or a comet lander.

(Note: The missions listed above are possibilities.  At least some of them probably would prove too expensive for the mission class suggested.)

One advantage of a program built on smaller missions is that if budgets are cut or one mission has to be cancelled because of cost overruns or technical difficulties, a robust program remains.

Con: None of these missions is likely to revolutionize our understanding of the solar system or to find an abode of past or present life.  The Mars sample return and Jupiter Europa Orbiter missions have remained at the top of the priority list for solar system exploration because they offer the chance for a revolutionary discovery.

What's my take on the options?  A program that focused on any of these elements can be justified in terms of scientific return for dollars spent.  A Mars sample return mission is a high risk/high return proposition, because it could consume the budget for a decade only to fail because of eventual political cancellation or because one of the many critical mission stages ends in disaster.  Combining the Jupiter Europa Orbiter with several New Frontier and Discovery missions would be a less risky approach, but would leave key questions about Mars -- the most Earth-like world -- unanswered.

It will be very interesting to see how the Decadal Survey resolves these problems.  The Survey members could go for a compromise that funds the first element of the Mars sample return mission (the ~$1.9B sample acquisition rover), the Jupiter Europa orbiter, and a modest New Frontiers and Discovery program.  Or they could decide to radically restructure the shape of the program and bet big on Mars or to go only with smaller missions.  The Nature article suggests that we may see the first draft of the proposed plan this Fall.

Why I Favor EJSM and Focused Exploration

As with all my editorials, I am not trying to convince anyone to my point of view.  No one on the Decadal Survey has ever heard of me, and my opinion counts for no more than any of the readers of this blog.  Rather, I find that reading a good editorial (and I hope my efforts are 'good') helps me focus my own thinking and reach my own conclusions.  So, with that in mind, here is one of the rare editorials on this blog.

In the next few months, the Decadal Survey will have to select missions to recommend for flight in the coming decade (2013-2022).  We have already been warned that sticker shock is coming and that fewer missions can be flown than advocates and scientists would hope.  At $3.2B and perhaps $4B with inflation and cost increases, the Jupiter Europa Orbiter would consume a substantial chunk of that ~$12-13B budget.  (ESA's Jupiter Ganymede Orbiter, if selected, would be paid for out of Europe's budget for its next large science mission.)  Perhaps most damning, funding EJSM would preclude funding for a flagship mission to Titan and Enceladus. 

My first reason for favoring EJSM is that it would explore three classes of important objects: (1) icy moons that may be habitats of life either in our solar system or others, (2) a large gas giant that is our best analogue for the many gas giants found around other stars, and (3) an intense magnetospheres that serves as a surrogate for other such structures in the universe.  The last two points speak for themselves, but I will expand a bit on the first point.  I believe that the ultimate exploration of an icy moon environment will be at Titan, but that world has such active surface processes that untangling its geologic history will prove difficult.  At Jupiter, we have four moons that provide case studies a range of tidally influenced moons (with Io and Callisto at the extremes) without the confusion of active surface processes.  Finally, Europa may be a habitat for life, and we should explore that potential with a highly capable spacecraft.

My second reason for favoring EJSM is that the JEO mission is ready to fly.  A decade of technology development and mission design has brought the mission to a point where risks are low.  We learned last year in the shoot out between EJSM and the Saturn Titan System Mission (TSSM) that the same was not true for concepts to explore the Saturn system (click here for the orbiter and here for the in situ elements). 

My final reason for favoring EJSM is the lesson learned from Mars exploration in the last decade.  At the Red Planet, we have learned that a series of highly capable missions can together bring a deep insight into a world or, in the case of Jupiter, a system of worlds.  NASA's JEO could be just the most capable of a fleet of craft that could also include ESA's Jupiter Ganymede Orbiter, Japan's magnetosphere orbiter, Russia's Europa lander, and possibly penetrators for Ganymede and/or Europa from another space agency.  Together, this flotilla would do for the Jovian system what a decade of missions have done for Mars.  What we learn from the Galilean moons will build towards our understanding of ice-ocean-rock moons including Titan and Enceladus.

Of these three arguments, I personally find the final most compelling.  We have done most of the easy missions for the solar system.  Significantly deepening our understanding of key worlds and systems will require focused exploration.  (Even if JEO turns out to be the only mission to fly to Jupiter, it is capable enough that it would count in my opinion as focused exploration.)  In the coming decade, I favor focused exploration on three and a half targets.  First, there will continue to be Mars which is likely to receive several orbiters from Russia, China, and ESA/NASA, 2-3 rovers, and possibly a network of science stations.  Second, could be the Jovian system.  And third, there could be Venus which could be the recipient of Russian and American landers, a European balloon platform, and several orbiters.  All in all, the next decade, thanks to the combined contributions of a number of space agencies, could see the in-depth exploration of the solar system expand from one target (Mars) to several.

The half target in my scenario would be the Saturn system.  Eventually, we need to return there with flagship class spacecraft.  I found the case laid out for a flagship class orbiter to take the global study of Titan to the next level in the TSSM study compelling.  Not only will a battery of instruments be required, but a high power communications system (which drives the need for a flagship class spacecraft) is essential to return the data stream.  However, there are, I think, a couple of low hanging fruits available for the Saturn system.  The first is Enceladus, for which a New Frontiers-class mission with with advanced instruments should provide a significant advancement in our understanding.  The second is in situ probes for Titan, which is about the easiest place in the solar system to land on or fly or float above.  The proposals in progress for a Discovery-class lake lander and a Discovery-class airplane suggest that in situ Titan probes could be within the budgets and technical capabilites of several space agencies in the coming decade.  The key problem for most in situ probes is the data communications challenge -- there simply isn't room within these probes to house the power systems and antennas to return large amounts of data.  So, I favor a New Frontiers class orbiter that would switch between focused Enceladus studies and relay duties for Titan in situ probes over the course of perhaps a decade or more in orbit around Saturn.

For the past year, I have closely followed the Decadal Survey process as well as the planning processes of other space agencies.  In this blog entry, I lay out the conclusions I've reached.  I hope that the readers of this blog will lay out their own or challenge mine in their comments.

Mars III workshop and goals for planetary exploration

The Mars III workshop was help at the end of March into early April.  Unlike many conferences, this one didn't focus on the latest findings reported in 15-20 minute presentations.  Instead, this workshop was a synthesis with a goal "to integrate the main results of both the recent Earth-based observations and the missions to Mars (MarsExpress, Mars Reconnaissance Orbiter, Phoenix and Mars Exploration Rovers) into a new global picture of Mars evolution."  As such, the presentations that are posted are fantastic tutorials on a wide range of topics, from the geological history, to the climate, to the interior structure.  Typical presentations (presumably with time for questions) lasted one-and-a-half hours.  A series of hour long presentations on current and recently ended (Phoenix) missions and thirty minute presentations on future missions rounded out the program.

If you are interested in Mars, this is a great place to spend some time.

I found three slides in the introduction presentation by Jack Mustard, particularly interesting.  The two following slides present key questions that dominated the field ten years ago and the key questions that dominate the field today.  Note how little overlap there is.  The past decade of exploration has done a great job of answering what had been the key questions, but of course that just led to new questions for the coming decade.  The exception to this story was studies of the Martian interior which largely will remain on hold until a network of geophysical landers is eventually flown.  (The presentation on network missions gives the long and sad history of attempts to get a network mission flown.  Best current hope is for a mission around 2020, assuming that it once again is not bumped to fund higher priority missions.)

The third slide from Mustard's presentation provides the goals for exploration of the terrestrial worlds (which would in this context include the other half of our double world system, our own moon).  All are key questions to understanding the evolution of our own world.  I am beginning to feel that the goal for the next decade of exploration should be twin focuses on the terrestrial planets (with Mars receiving the bulk of the money and attention, but significant missions to Venus and/or the moon) and on the icy moons of Jupiter and Titan as possible abodes of life.  Perhaps $5B to each set of missions, leaving ~$2B for Discovery class missions to asteroids and comets.  While this would leave many missions I would very much like to see fly such as the Io Volcano Explorer and the Argo Neptune-Triton flyby, the success at Mars in answering a string of high priority questions in the past decade shows the power of focusing exploration.

Link to Mars III workshop presentations: http://sci.esa.int/workshopmars3

Decadal Survey Update: Sticker Shock Ahead

Steven Squyres has been presenting updates at various planetary science conferences on the status of the Decadal Survey.  The slide above is from his most recent presentation at an astrobiology conference.  (You can down load the entire presentation by going to the Decadal Survey webpage and scrolling down to 'Past outreach events, and clicking on the 'Astrobiology Science Conference' presentation.  Sorry, no url to the presentation itself.)

Other than these updates, formal news from the Survey has been scarce.  Each of the working panels have been meeting over the past month in closed session to work on their reports.  Several news articles, including one in the subscription only version of Aviation Week and Space Technology, have been touting the search for present and past life as an overarching theme likely to emerge from the Survey.  (See a summary of the Aviation Week article here or the Space Daily article.)

Each of the science panels (inner planets, Mars, giant planets, etc.) has been including science goals that link to astrobiology (See slides at end of this blog entry from Squyres' presentation).  For Mars and the outer planet satellites, this is easy since they include habitats that could be past or present abodes of life.  For the inner planets and primitive bodies, the goal is to tie into the evolution of habitable worlds.  Only the giant planets has not been able to find a tie to astrobiology.

The Aviation Week article lists several missions that best tie to an astrobiology theme; I've included possible costs that I've read in the past, but not Squyers' warning about sticker shock.  (Note, for the purposes of the Survey, the decade runs from 2013 through 2022.)

• Mars Trace Gas Orbiter - $500M?
• Mars Sample Return (series of three missions) - $5-7B, with perhaps $4B needed in coming decade
• Jupiter Europa Orbiter - $3B
• Titan/Enceladus missions - wide range of costs depending on sophistication
• Comet sample return - at least $1.2B if warm samples (i.e., the ices melt) are allowed

Add this up, and assume 2-4 Discovery missions for those destinations without an astrobiology tie, and this would pretty well fill the expected budget of $12-13B over the decadal period (FY11 dollars).

One of Squyres' slides showed a schedule for the Survey's meetings.  It showed that the results of the analyses of candidate missions will be available to the Survey in July of this year.  It's not clear when those results will be made public.

I've gone through the list of missions under consideration by the Survey and listed them based on tie to an astrobiology theme.  (Some of the missions listed as non-astrobiology could associated with some astrobiology theme.  Feel free to disagree with my assignments!)  Institutions listed after each candidate mission indicate which institution is preparing the analysis of that mission.  Costs will be independently assessed.

Astrobiology

• Mars Trace Gas Orbiter (JPL)
• Mars Polar Mission (JPL)
• Mars Sample Return (JPL): (Mars Astrobiology Explorer with Cacheing (MAX-C rover), Mars Sample Return Lander, Mars Sample Return Orbiter)
• Europa Flagship Mission (JPL)
• Titan Flagship Mission (JPL)
• Titan Lake Lander (JPL)
• Enceladus Mission (JPL)

Evolution of [potentially] habitable worlds

• SAGE Venus orbiter (NASA NF-3 Candidate)
• Venus Mobile Explorer (GSFC)
• Venus Tessera Lander (GSFC)
• Venus Climate Mission (GSFC)
• Ganymede Mission (JPL)
• OSIRIS REX asteroid sample return (NASA NF-3 Candidate)
• Comet Surface Sample Return (APL)

Non-astrobiology Missions

• Moonrise lunar sample return  (NASA NF-3 Candidate)
• Lunar Polar Volatiles Lander (APL)
• Lunar Network Mission (MSFC)
• Mars Network Mission (JPL)
• Io Mission (JPL)
• Saturn Probe (JPL)
• Uranus System Mission (APL)
• Neptune System Mission (JPL)
• Main Belt Asteroid Lander (APL)
• Chiron Orbiter (GSFC)
• Trojan Asteroid Tour (APL)

In another area of Squyres' presentation, reemphasized that only missions that already flying or have formal new starts are excluded from the Decadal Survey's review.  The missions in development that have formal new starts, plus the next New Frontiers selection (since the selection is in progress) are listed below:

Missions still to launch not included in Decadal Survey:

• Juno (Jupiter) 2011
• Mars Science Lab 2011
• Maven (Mars aeronomy) 2013
• Artemis (Lunar fields and particles) 2011
• GRAIL (Lunar gravity) 2011
• LADEE (Lunar atmosphere and dust) 2012
• Next New Frontiers mission (OSIRIS-Rex asteroid sample return, SAGE Venus lander, or MoonRise lunar sample return)

The following slides are from Squyres' presentation and list the science goals of each sub-discipline (astrobiology goals are presumably highlighted since Squyres was presenting at an astrobiology conference).

Europa vs. Titan Redux?

The presentations at the February OPAG meeting held statements that the Europa versus Titan decision may come back up for review. Last year, two teams competed to be selected for the next NASA Flagship mission and for a place in ESA's next large mission competition.  The review teams concluded that the science from either mission would be equally good, but that a decade of technology development made the Europa mission much more ready for development than the Titan mission.  A NASA Europa mission got the nod and an ESA Ganymede orbiter won a spot to compete against two astronomy missions (with the ESA decision to come next year).  Both space agencies promised to fund advanced mission planning and technology development to make the Titan mission ready for its own start later in the decade.  [Editorial note: The Survey could decide not to prioritize missions to either Europa or Titan, but I wouldn't take a bet on that outcome.]

Now, that decision on the American side is up for review as part of the Decadal Survey.  NASA has made it clear that it will take its priorities for planetary missions in the coming decade from the Survey's priorities.  Any mission that has not received a formal new start from Congress must be recommended by the Survey for NASA to procede.  That includes the Jupiter Europa orbiter.  

NASA's current budgets continue to fund the Jupiter-Europa for Phase A, which is the period of advanced development before final design, manufacture, and testing begin.  Funding beyond Phase A is contingent on the Decadal Survey making this mission a priority.  To do that, the Survey would have to deprioritize other elements in NASA's current roadmap.  At $3.2B, there simply isn't room in the budget for this mission and the current Mars program and the New Frontiers and Discovery programs (see here for analysis of latest NASA budget proposal).

At the same time, the proponents of Titan as the choice for outer planet exploration are working to be making their voices heard.  One of them, Ralph Lorenz, presented at the meeting.  He showed that Titan has been to subject of many more scientific articles than has Europa over time. (To be fair, the Cassini-Huygens mission has returned far more data on that moon than the crippled Galileo spacecraft did for Europa.)  He also complained that promised funding for advanced development of a future Titan mission has not been forthcoming.  As an example, he described how promised money to develop balloon technology for a Titan mission had gone instead to fund the Decadal Survey.

Cassini's continued exploration at Titan continues to build the case for returning to that world and to neighboring Enceladus.  The case also is being made that Titan could be home to exotic forms of life and one scientific paper has prioritized Titan ahead of Mars as the best place for astrobiological exploration in the solar system (Europa came in third).  Recent finds at Enceladus continue to build the case that that moon has an internal ocean that could host life.

Whether to return to Europa or Titan or both or neither in the coming decade looks to be one of the biggest decisions facing the Decadal Survey.

Editorial Thoughts: Europa-Jupiter and Titan-Enceladus-Saturn both are compelling targets for exploration.  Both destinations should be explored in the coming decade.  However, the radiation belts at Jupiter impose significant technical challenges to any mission that will meaningfully answer the question of whether Europa could be explored for life, either by finding a thin point in the ice to penetrate or by finding a location where recent eruptions have brought ocean material to the surface.  On the other hand, Titan-Enceladus-Saturn presents a relatively benign environment (if a bit chilly within the atmosphere of Titan), but the mission design and technology apparently aren't ready to fly for some of the most exciting mission concepts.

If the decision were up to me, I would commit to the $3.2B Europa-Jupiter mission and budget another $2B for Titan-Enceladus-Saturn, which might be expanded if other space agencies contributed.  I'd go ahead with the Jupiter Europa Orbiter as planned -- it's ready to go and the harsh environment at Europa doesn't favor cheap missions.  It would also do for the Jupiter system what Cassini is doing for the Saturn system and what Galileo with its crippled antenna couldn't.  Around $2B probably would fund a highly capable orbiter or a less capable orbiter (perhaps similar in scale to the proposed Io Volcano Observer)  and a Titan in-situ probe such as a lake lander.  


An alternative strategy would be to commit ~$3B to Titan-Enceladus-Saturn, perhaps for a combination of New Frontiers scale missions.  Perhaps a Saturn orbiter could execute a number of flybys of Titan and Enceladus with  instruments tuned to fill gaps in Cassini's investigations.  The orbiter could also act as a relay for one or two in situ Titan craft, perhaps the Titan Mare Explorer and the aerial AVIATR.  The Europa-Jupiter mission would then be constrained to a $2B mission.  Within that budget, a capable craft could perform a number of flybys of all the Galilean moons, study Jupiter from afar, and perhaps orbit Europe for weeks instead of the months planned for the Jupiter-Europa Orbiter.  However, the orbiter missions under investigation by the Decadal Survey do not currently include alternatives to the Flagship, ~ $3B, Europa Jupiter System Mission and the Titan Saturn System Mission for exploring those two moons.  The Survey is looking at a number of mission concepts to explore Enceladus, a Titan Lake lander, a Ganymede observer, and an Io observer.

Either of these plans could leave ~$5B for Mars exploration, which would fund the Mars Trace Gas orbiter and the 2018  ExoMars/Max-C mission and leave ~$2.5B for other Mars missions, presumably down payment on a sample return.  In this scheme, lunar, inner planet, and small body exploration would have to share the remaining ~$2B, which would fund perhaps a Discovery mission and a New Frontiers mission.

Baring breaking news on future planetary exploration, the next two blog entries will look at the planning for the science that the Jupiter Europa Orbiter could do for Jupiter and the Galilean moons other than Europa.

Resources:


Updates on NASA outer planets program and status of Jupiter Europa Orbiter funding from Feburary OPAG meeting

• Planetary Science Division Program Status
• Outer Planets Program Status

Ralph Lorenz's OPAG Presentation on status of Titan mission planning

Space News article on possibility of life on Titan http://www.space.com/scienceastronomy/titan-water-life-am-100323.html


Paper prioritizing Titan for astrobiology missions, The Search for Alien Life in Our Solar System: Strategies and Priorities

Decadal Survey Update

I've been busy with various projects so that recent posts have focused on process which are quicker to write.  Within the next week, I'll start posting again on possible future missions.

At the just completed Lunar and Planetary Science Conference Steve Squyres provided the most complete explanation and update of the Decadal Survey I've seen yet.  (Go to the Decadal Survey webpage, and look for 'View the Presentation given by Decadal Chair Steve Squyres to the LPSC on the status of the study' about a quarter of the way down the page.  This is a Java link, so I can't provide a normal link.)

His presentation discusses the scope of the Survey, which will prioritize all Flagship and New Frontiers missions.  If New Frontiers missions are prioritized by rank as opposed to just identifying a candidate pool of targets, this will be change in how these missions are selected.  The last Decadal Survey selected a pool of (if memory serves me correctly) four missions that was latter expanded to six to eight missions.  Any target within the pool -- which ranged across the solar system -- was an allowable target.  Squyres' slide suggests that instead, this Survey may actually designate which specific targets are priority #1, #2, and so forth.

Discovery missions will continue to be selected by competition, but the science goals by which they will be selected will be identified by the Survey.  Only missions that have received formal budgetary new starts and therefore are in development are exempt from review (these are Juno [Jupiter interior and atmosphere], GRAIL [lunar gravity], Mars Science Laboratory rover, LADEE [lunar atmosphere], MAVEN [Mars upper atmosphere]).  All other missions including the Mars Trace Gas orbiter and the Jupiter Europa Orbiter are subject to Survey review and prioritization.  A key requirement is that the recommended list be able to be implemented within expected budgets.  NASA has made it clear that it will use the Survey's prioritization as its priorities.

Squyres included a schedule for completing the survey:

2010

• 1st- 2nd Quarter Final Panel meetings, Panel reports finalized
• 2nd-3rd Quarter Prioritization and drafting of survey report
• 4th Quarter Draft survey report to reviewers, Report revised

2011

• 1st Quarter Report approved, NASA, NSF, OMB and Congress briefed and report released (prepublication-format)
• 3rd Quarter Printed report released

Editorial Thoughts: The presentation suggests a difference in the way New Frontier missions are selected.  In the past, they have been selected from a list of missions.  In any given decade, only a third (and later after the list was expanded a quarter) of the missions could be selected.  If the survey is prioritizing New Frontiers missions, the list of missions would likely be constrained to just those that could be afforded within the coming decade.  It is also possible that the Survey will recommend one or more small Flagship missions at around $1 - 1.5B (compared to ~$3B for a full scale Flagship mission).  If this occurs, the coming decade could have a much more focused program than the last decade.

A couple of weeks ago, the subscription-only journal Nature had an article discussing the Astronomy Decadal Survey, which is in progress but somewhat ahead of the Planetary Decadal Survey.  Nature held a round table with several prominent astronomers who were not members of that Survey.  The participants emphasized the importance of a 'narrative' to provide a story behind the recommendations of a Survey.  The search for life in the universe and understanding the origins of the universe were discussed as possible astronomy narratives.  (As a side note, a strawman poll of the Nature discussion participants gave priority to the Large Synoptic Survey Telescope, the Giant Segmented Telescope, the Terrestrial Planet Finder, and the Constellation-X Observatory/International X-ray Observatory.)

If the planetary survey selects a narrative, then prioritizing the larger Flagship and New Frontiers class missions makes sense.

I don't think it's hard to predict a likely Planetary Survey narrative: The search for possible habitats for life, past or present, in the solar system.  This would give priority to missions to Mars, Europa, Titan, and Enceladus.  Venus, Ganymede, and Callisto might gain supporting roles as worlds that help us understand the evolution of terrestrial planets and icy moons.  If this becomes the narrative, the target worlds are easy to predict.  What is harder to predict is how the Survey will recommend that dollars and therefore mission resources be divided between them.

Appendix: This is the list of missions that the Survey is considering for the next decade (from Squyres' presentation). The institution performing the analysis of each mission is also given: Goddard Spaceflight Center, the Jet Propulsion Laboratory, the John Hopkins Applied Physics Laboratory, and the Marshall Spaceflight Center.

• SAGE (NASA New Frontiers 3 Candidate)
• Venus Mobile Explorer (GSFC)
• Venus Tessera Lander (GSFC)
• Venus Climate Mission (GSFC)
• Moonrise (NASA New Frontiers 3 Candidate)
• Lunar Polar Volatiles Lander (APL)
• Lunar Network Mission (MSFC)
• Mars Trace Gas Orbiter (JPL)
• Mars Polar Mission (JPL)
• Mars Network Mission (JPL)
• Mars Sample Return (JPL):
• Mars Astrobiology Explorer with Cacheing
• Mars Sample Return Lander
• Mars Sample Return Orbiter
• Europa Flagship Mission (JPL)
• Io Mission (JPL)
• Ganymede Mission (JPL)
• Saturn Probe (JPL)
• Titan Flagship Mission (JPL)
• Titan Lake Lander (JPL)
• Enceladus Mission (JPL)
• Uranus System Mission (APL)
• Neptune System Mission (JPL)
• OSIRIS REX (NASA New Frontiers 3 Candidate)
• Main Belt Asteroid Lander (APL)
• Chiron Orbiter (GSFC)
• Trojan Asteroid Tour (APL)
• Comet Surface Sample Return (APL)

Additional Studies

• NEO target study. (Assess NEO targets that can be reached with an electric propulsion spacecraft.)
• Reactor-Based thermoelectric generator technology study.
• Saturn Ring Observer technology study.
• Comet cryogenic sample return technology study.

Beyond describing a prioritized set of NASAplanetary missions, the survey report will address several other issues:

• NSF-funded ground-based telescopes
• Technology development for future NASA
• planetary missions
• The NASA and NSF planetary R&A programs
• Education
• Public Outreach

Decadal Survey Update

Steve Squyres has just published the January update for the Decadal Survey.  I'd characterize the current efforts as laying the foundation for the eventual plan.  Like laying the foundation for a building, this isn't the glamorous work, but without it, the edifice won't stand.  Three sets of activity are underway:

The steering committee has been focusing on two key threats to the ability to carry out a robust program: the rapidly escalating cost of launch vehicles and the plutonium-238 shortage.  Later this winter it will look at the technology development program.

The panels (each focuses on a group of destinations, for example Mars or the outer planet satellites) are nearing completion of their assessments of the key science goals for the next decade.  Eventually, once these lists are merged, these goals will be used to prioritize a set of missions.  Their reports, if memory serves me right, are due out this spring.

In parallel with the goals assessments, 21 mission concepts are being defined and/or having cost estimates prepared.  This effort will lead to determining which concepts are technically ready and can fit within the budget.  Since the last update, one new concept has been added, a Venus Tessera Lander.  While lowland Venus lander studies already were underway, this study focuses on how to land in the rugged highlands of Venus.

---------------------------

Monday will see the release of the President's budget proposal for fiscal year 2011, including for NASA's planetary program.  I'll publish an analysis Monday evening or Tuesday morning.  Then later next week I'll publish an entry on missions to study the trace gases in the Martian atmosphere.

My Stab at a Decadal Priority List

We're in a bit of a hiatus in terms of Decadal Survey news.  The next round of meetings for the discipline panels (e.g., Inner Planets) aren't scheduled to occur until April and May.  The Steering Committee will meeting in late February, but it appears to be focusing primarily on enabling technologies.

I've been following the Survey's progress probably as closely as anyone outside of the process has.  During the last few months, I've been wondering what criteria I would use to set priorities.  And that led me to thinking what priorities would I choose.

I want to emphasize that what follows isn't an attempt to persuade anyone about what the priorities should be.  Your opinions are as valid as mine, and except for perhaps a lucky one or two readers who may be involved in the process, your and my opinions are likely to have the same impact.  However, I often learn more from a carefully crafted argument than I do from just reading the facts (which is why I read the opinions page of the newspaper more regularly than the front page).  So here goes (and I hope that you find this carefully crafted).

A successful program has to meet a number of goals:

1. It must be fiscally possible.  That is, it has to fit within the $12-12.5B budget expected for the next decade.
2. It must be compelling to the public and to the politicians who will have to prioritize dollars spent here over other worthy projects over the course of a decade.
3. It must significantly advance our scientific understanding of the solar system.
4. It should provide a balance between types of solar system bodies.  The list of discipline panels suggests the breadth possible: Inner planets, Mars, giant planets, outer solar system satellites, and primitive bodes

There's another criteria that may or may not be adopted by the Survey, but I think should be.  It is quite possible that over the course of the decade that the budget for planetary exploration may be cut.  (Recent reports that NASA will not receive a $1B budget boost for the next fiscal year leads credence to this fear.  Planetary missions will be in competition with the politically popular manned and Earth observation programs.)  I believe that the prioritized list of missions should remain useful if budget cuts occur.

I think that the most critical decision the Survey will face will be setting the balance between the large Flagship missions and smaller New Frontiers and Discovery class missions.  Two Flagship missions are likely candidates, Mars Sample Return (MSR) and the Jupiter Europa Orbiter (JEO).  These missions are large enough that they together would chew up three quarters of the budget.  However, it could be argued that these two large missions would provide the greatest scientific return of any missions on the candidate list.  There would also sufficient budget to fly the Mars Trace Gas Oribiter, support the ExoMars rover (as part of MSR's MAX-C rover), and fly three smaller missions which could visit the inner planets and primitive bodies (MSR and JEO would take care of Mars, the giant planets, and outer solar system satellites).

Example of a priority list and budget for a program that emphasizes Flagship missions.  Figures are in $Bs, and use either published estimates or my own best guesses.  New Frontiers and Discovery figures include the PI budget (~$650M and ~$450M) plus launches and other overhead.

I have two concerns about this priority list.  First, MSR and JEO could easily experience large cost overruns that prevent missions to other destinations.  Second, large missions make tempting targets for politicians looking to cut budgets.  Both of these missions would have to find political support across at least two Presidents and about a half dozen Congresses.  (In America, we elect the entire House of Representatives and a third of the Senators every two years, which counts as a new Congress (even though the reelection rate is so high that 'new' may be a misnomer).)  The counter argument is that scientific support for these big missions would be great enough to shield them from cancellation.  There's some truth to this (look at the survival of the James Webb telescope and the Mars Science Laboratory despite massive overruns).  On the other hand, a number of large science programs have been cut in the past; remember the Comet Rendezvous and Asteroid Flyby (CRAF) sister ship of Cassini cut in the early 1990s.

I instead prefer a priority list that focuses on smaller missions to many solar system targets.  Then if budgets permit, I would fly the full JEO mission and the first component of MSR, the MAX-C rover, as the lowest priorities.  This way, if budgets are cut, there is still a robust program of missions to a number of destinations.

How I would prioritized my list of missions based on mission concepts that have been studied to date.

While this list may seem like a scattered set of missions, there are some themes.  Mars remains the top priority with over a third of the budget.  Icy moons would be a priority with missions to the Jovian moons, Titan, Enceladus, and Triton.  The single Venus mission looks lonesome, but I see it as the NASA contribution to an international flotilla to that world.  However, the primitive bodies scientists would rightfully feel left out with just a single Discovery mission.  (I left both the Venus and primitive bodies missions as placeholders.  Depending on which missions are selected in the current New Frontiers and Discovery competitions, the priorities for these missions may change.)  It was really hard leaving off some missions I really like and that would produce great science like the Io Volcanic Observer (IVO).  (However, I could imagine a scenario where a line of New Frontiers class spacecraft were built using nearly identical spacecraft for the JMO, TEO, and Argo missions and then the savings might fund IVO.)

You'll note that I don't specify specific targets for several Discovery and New Frontiers class missions.  I have concerns about the totally open competitions to date, which make it impossible to know which missions will fly.  A consequence of this is that NASA has a harder time prioritizing its technology development funds.  If, however, NASA knows that it will be flying a lander to Venus, it can prioritize the appropriate development work.  Prioritizing specific targets also makes it easier to put together international collaborations.  If NASA will be flying a Titan/Enceladus observer, then perhaps another space agency would fund a Saturn atmospheric probe or a Titan lander to ride along.

As I said in the beginning, there's nothing special about my list.  However, I hope that it will get you to thinking about what priorities you would set.

Oh, and as the Survey studies additional mission concepts, it is likely that my list of priorities will change.  There's a number of exciting concepts under study.