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One key to understanding the recommended program is that the Survey's members sought balance.  While Mars has dominated NASA's program for over 15 years, the goal going forward was to have a balanced program.  There are a couple of ways to look at balance.  One is by type of target -- inner planet other than Mars, outer planets, primitive bodies, etc.  Another way is by the method of study: remote sensing of surfaces or atmosphere, measurements within an atmosphere, measurements on the surface, measurements within a magnetosphere, sample return.  The latter approach is often more telling than the destination.  An atmospheric chemist, for example, can switch between Venus, Titan, or Uranus, but is left out on a lunar mission.

With that in mind, how do the recommended missions compare by target and type of study?

Among the Flagship missions, the Giant Planets were a clear favored destination.  This isn't surprising.  Mounting missions to these distant worlds in inherently expensive and once that initial cost is assumed, the inclination is to fly more capable missions that require Flagship (>~$2B) funding.  Among the New Frontiers candidates, however, there are no clear winners.  Candidate missions are well distributed by type of destination and by type of study.  I believe that the goal of achieving this balance explains why a near Earth asteroid sample return mission was dropped from the list (although it remains a candidate for the selection in progress).  Including it would have meant too many primitive body missions and too many sample return missions.

(I want to emphasize that the chart above has been simplified to focus on major types of study.  The Venus Climate Mission, for example, would include a camera on the orbiter for context images, but this would not a major focus of the mission.  On the other hand, the Comet Sample Return mission has to have capable remote sensing instruments to select landing sites and would make a major contribution to our understanding of the surface of these bodies even though the focus of the mission would be on the sample return.  I also chose to count the Enceladus orbiter as making an "atmospheric" measurement within that moon's plumes, but counted measurements of the near-vacuum atmospheres of Europa and Io as magnetosphere studies.  Please forgive any oversights.)

It's also interesting to look at the program in terms of financial balance.  The Survey members stated that they did not want a single mission to dominate the program.  Here is a list of the estimated mission costs in the Survey report with acceptable costs in parentheses if the full cost was unacceptable:

Flagship missions not recommended
Titan Saturn System Mission $6.7B
Jupiter Europa Orbiter $4.7B
Mars MAX-C and ESA ExoMars rovers $3.5B

Flagship missions with high priority
Descoped Mars rover mission $2.5B
Descoped Europa mission (cost target not given)
Uranus Orbiter and Probe $2.7B

Flagship missions with lower priority
Enceladus Orbiter $1.9B
Venus Climate Mission $2.4B

New Frontiers mission candidates
Lunar Geophysical Network $1.3B
Io Observer $1.4B
Trojan Tour $1.3B
Saturn Probe $1.3B
Comet Surface Sample Return $1.5B

(Cost estimates were not given for the Venus lander and lunar sample return missions; since both have proposals in competition for the next selection, it was assumed their costs would fall within the present New Frontiers cost cap.)

From this list, it appears that Flagship missions around ~$2.5B were acceptable because they would each represent less than a quarter of the then presumed funding for new missions.  (Under the new funding outlook, none can be afforded except for a possible even more descoped joint rover mission with ESA.)

Interestingly, the additional New Frontiers candidate missions all exceed the recommended budget of $1B per mission for candidates selected mid decade and beyond.  The Survey chair, Steve Squyres, has said that they believed that clever proposing teams will find ways to fit several of these missions within that budget cap.   These missions at these prices may represent a new class of mission.  Previously, the principal investigator's budget for the craft, instruments, and operations was capped at ~$650M; the new proposed cap at $1B represents a significant increase in funding per mission.

The Juno mission to Jupiter is scheduled to launch this coming summer.  Aviation Week and Space Technology just published two articles on the mission, one focused on design and implementation and the other on the science.  Normally, AWST requires a subscription to read, but both articles are posted on public websites.

The science article is posted on AWST's website.  The other, longer article, appears to be available on the Zinio website, which provides an electronic subscription service to magazines and other media.  I subscribe to AWST through Zinio, so it is possible that the link to this article may not work for those without the subscription.

Following the release of the planetary Decadal Survey, I’ve discussed the need for missions in the coming decade to be highly focused to fit with fixed cost caps.  Nowhere will that need be greater than for outer planet missions to explore the icy-ocean moons.

For me, there were two major surprises in the Decadal Survey.  The estimated costs of missions, especially the Flagship missions, stunned me.  As I’ve had a week to think about the Survey, though, the bigger surprise has been the lack of focus on the icy-ocean worlds.  Perhaps there is no way to meaningfully explore Europa given limited budgets and its location deep in Jupiter’s radiation belts – perhaps only the surface of Venus is a more hellish location for spacecraft.  Titan and Enceladus are comparatively easy to explore, and their major drawback for further exploration is the many years needed for a spacecraft to reach them.  (I heard in a conference this week that operating a spacecraft during cruise costs $7-10M a year, and Saturn can take up to seven years to reach.)  Cassini’s discoveries at these two moons, in my opinion, however, put them on the short list of the highest priority worlds to explore.

I believe that the Survey’s members concluded that the cost of incremental missions to these moons for the science they could return would be too low to make them priorities.  They prioritized a $2.9B Uranus mission to begin the in-depth exploration of the ice giant worlds over a $1.9B Enceladus orbiter.  As budget projections stand, we are likely to get neither.

A Discovery mission to the outer planets would set a new cost-return point that might be quite attractive.  At least two Discovery-class missions have been proposed for missions to Titan or Titan and Enceladus.  The proposers are attempting to implement missions that would be approximately half the cost or less of equivalent missions briefly studied by the Decadal Survey.  However, several observers have pointed out that the Decadal Survey mission concepts tended to have rich payloads, weren't optimized to reduced costs, and were made under conservative design and cost assumptions.

I don’t know if the Discovery budget (perhaps ~$800M with launch) can enable missions to explore the outer solar system.  While the proposers of the three outer planet Discovery missions I know about (Io Volcano Obersver, Titan Mare Explorer, and Journey to Enceladas and Titan) have a great deal credibility, mission champions have also been known to be too optimistic.  I hope they succeed.  It is instructive, however, to look at the tradeoffs that might enable an outer planets Discovery mission.

The Decadal Survey examined an Enceladus orbiter that would also make a number of Titan and other moon flybys.  That mission would carry five instruments and involve a complex 4-4.5 years of moon flybys and orbital operations.  By comparison, the Journey to Enceladus and Titan (JET) Discovery proposal would have just two instruments and one year of operations.  The Principal Investigator for the proposal, Christophe Sotin, was kind enough to give me permission to reprint his team’s abstract on the mission from the just completed Lunar and Planetary Science Conference.  This abstract both shows how Discovery missions to the outer planets must have limited goals and shows how they may be able to still address interesting science.



JET: JOURNEY TO ENCELADUS AND TITAN
C. Sotin1, K. Altwegg2, R. H. Brown3, K. Hand1, J.I. Lunine3, J. Soderblom3, J. Spencer4, P. Tortora5, and the JET Team, 1Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove drive, 91109, Pasadena, CA, 2University of Bern, Switzerland, 3University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ, 4Southwest Research Institute, Boulder, CO, 5Universita di Bologna, Italy.

Introduction: The Cassini-Huygens mission has demonstrated that Enceladus and Titan represent two crucial end-members in our understanding of planet/moon formation that might have habitable environments. Enceladus is a small icy world with active jets of water erupting from its surface (Fig. 1) that might be connected to a subsurface water ocean. Titan is the only moon with a dense atmosphere and the only object besides Earth with stable open bodies of liquid on its surface (Fig. 2). An organic-rich world, Titan has a methane cycle comparable in atmospheric and geological processes to Earth’s water cycle.





The questions that JET would answer directly respond to the wealth of discoveries made by the Cassini- Huygens mission. High-resolution mapping of Titan surface is required to determine what processes have shaped and are shaping Titan. High-resolution mass spectroscopy would permit assessment of the astrobiological potential of Enceladus and Titan.

Concept: The JET mission has been proposed in response to the 2010 NASA Discovery Announcement of Opportunity. In order to achieve JET’s rich science return within the Discovery cost cap, a planetary orbiter with a simple, two-instrument, but powerful payload would make a total of 16 flybys of Enceladus and Titan. The only new technology is the NASAprovided Advanced Stirling Radioisotope Generator (ASRG) that would be validated as part of the Discovery Program’s engineering goals.

Along with making new observations of Enceladus and Titan, JET would fill a critical temporal gap in our understanding of the Saturnian system. Enceladus and Titan have near-equatorial orbits around Saturn, and Saturn has an inclination of 26º relative to its orbital plane around the Sun. Consequently, Saturn and its moons have seasons. Voyager briefly observed Saturn and its moons during the Saturnian Vernal equinox. Cassini observations extend from winter solstice to the summer solstice. JET would observe Titan during autumnal equinox, an opportunity that will not arise again until 2054. Observations during the Autumnal equinox are critical to understanding the fate of lakes and seas, Titan’s complex meteorological cycle, and the fate of organic molecules.

Science: The three goals of the mission are to determine the processes that have shaped and are shaping Titan, to assess the astrobiological potential of Enceladus and Titan, and to investigate the formation and evolution of Enceladus and Titan. These three goals are then detailed in eleven science objectives and thirty-one science questions that cannot be answered by the Cassini mission. Three examples are given. First, the Cassini mission has discovered that mass 28 in Enceladus’ plume has possible CO, N2 and/or hydrocarbon components. JET would confirm what fraction is CO vs. N2 vs. hydrocarbons. Second, the Cassini-Huygens mission has discovered that rivers and valleys are carved into plateaus and mountains. JET would search for sedimentary layering in valleys to determine the history of the flows. Third, Cassini has discovered that heavy molecules (m>100 Da) are produced in Titan’s upper atmosphere. JET would determine the nature of these molecules. This list of questions includes ten of the major discoveries of the Cassini mission that await a more capable mission to unveil the geological history and astrobiological potential of these two unique moons in the solar system. JET’s payload—a camera (TIGER [Titan Imaging and Geology, Enceladus Reconnaissance]) and a mass spectrometer (STEAM [Spectrometer for Titan and Enceladus Astrobiology Mission]—would provide the capability for achieving these science goals.

Instruments: The payload is limited to two powerful instruments and the radioscience investigation. The total data volume would be on the order of 120 Gb during the one year nominal mission.

STEAM: The reflectron time of flight mass spectrometer [2] is the Rosetta flight-spare of the Rosina mass spectrometer. It would characterize elements and molecules including complex organic molecules with a 10× larger mass range, 100× higher resolution, and 1000× better sensitivity than Cassini (Fig. 3). It would resolve fundamental issues related to the chemical composition of Enceladus’ jets and their relationship to the structure and evolution of Enceladus’ interior. STEAM would also characterize Titan’s organic-rich upper atmosphere.



TIGER: This high-heritage IR camera exploits four IR windows through Titan’s haze and would image the heat of Enceladus’ fractures (Fig. 4). This camera uses the 5 μm window [3] to provide 10× better imaging resolution of Titan’s surface than Cassini, yielding 50 m/pix images of 15% of Titan’s surface. At each Titan flyby, an area twice as large as France would be mapped at 50 m/pixel in addition to Titan full disk at 500 m/pixel. The 50 m/pixel resolution is achieved at 2250 km from Titan’s surface. Currently, only ~10-6 of Titan’s surface area was imaged at this resolution by the Huygens probe. JET would deliver a five order of magnitude increase in coverage of highresolution imagery of Titan’s surface. Similarly, TIGER would provide 10 m/pix images of selected Enceladus’ tiger stripe fractures, permitting detailed thermal modeling.



Mission: The mission would be launched in February 2016 and would be inserted into Saturn’s system in May 2023. The nominal one-year mission would start with 12 Titan flybys with the closest ones at 900 km from Titan’ surface. This distance would vary from one flyby to the other in order to sample different layers of the upper atmosphere. Both Saturn and anti- Saturn hemispheres would be mapped. The Titan phase would be followed by 4 Enceladus flybys to sample the different jets of the South pole. The nominal end of mission would be a Dione disposal. A 6- year science enhancement option would permit to get into Titan orbit, offering the opportunity to further test the ASRG and to relay data from any element present on Titan’s surface or in its low atmosphere at that time.

References: [1] Stephan K. et al. (2010) GRL, 37, L07104. [2] Scherer S. et al. (2006) Int. J. Mass Spectrometry, 251, 73–81. [3] LeMouelic S. et al. (2011) LPS XLII.

It turns out that I wrote my previous post about the process to plan for possible planetary partnerships between NASA and ESA a few hours too early.  Since I wrote that, two articles have appeared that give additional information, especially from the European perspective.

Amy Svitak (whose stories I have come to look forward to) at Space News writes a good summary of the issues focusing on joint Mars and Jupiter system missions.  She reports that industry bids for building ESA's ExoMars rover have come back higher than expected, giving ESA a possible additional incentive to continue a partnership with NASA to share costs.  (ESA originally sought a partnership because its previous cost estimates for the entire mission exceeded its budget.)

On the journal Science's website is a story that focuses on a new redefinition of ESA's three candidate missions for its next large science mission, one of which is the Jupiter Ganymede Orbiter (JGO).  All three candidate proposals depended on a partnership with NASA (and one on a partnership with Japan).  However, none of these missions were top-ranked candidates in the U.S. astronomy or planetary Decadal Surveys.  Given budget issues in both these programs at NASA, ESA has concluded that NASA partnerships are unlikely as previously envisioned.  (For JGO, the previous plan had been for NASA to fly its own complimentary Jupiter Europa Orbiter and contribute instruments to JGO.  NASA can no longer do the former, but still plans to offer to do the latter if JGO is eventually selected as ESA's next large mission.)  ESA has asked the three proposing teams to reexamine their proposals and rescope them as ESA-only missions.  The new mission proposals are due in a year.

James Green, director of NASA' Planetary Science program, included this one figure summary of the Decadal Survey's recommendations.  No new news, but a handy summary.  You can read the entire (short) presentation at http://solarsystem.nasa.gov/docs/Latest_Green_to_PSS_031611.pdf

The most important figure in the Decadal Survey report for me was buried at the back in Appendix C.  It was not until I read the journal Science's article on the survey (subscription required) that I realized its importance.

Before I get to that, it's been a week since we learned the key elements of the Decadal Survey through a Space News story based on a leaked summary.  We have been surprized by the cost cost estimates of the Flagship missions.  We heard in detail how the projected funding for NASA would support something like half the program recommended by the Survey.

During the past week, I've read most of the report and numerous summaries and commentaries on the report.  I've also watched the full question and answer period following Squyres's presentation of the report, the joint press conference with James Green, and Green's NASA update.  (Squyres was the chair of the Decadal Survey and James Green is the head of NASA Planetary Program.)

From Green's comments, it appears that it will be months and perhaps almost a year before we understand the full response to the Survey's recommendations and declining NASA planetary budgets.  Green, his staff, and the planetary community will take that time to scrub the budget, re-examine assumptions, think through mission costs, and negotiate with ESA on the 2018 Mars rover mission.

For now, though, here's what the picture looks like.  The first half of this decade will be a golden age of planetary exploration for NASA.  A number of missions are already in flight and will reach their targets or continue their studies.  Four NASA missions will launch in the next two years.  New Frontiers and Discovery missions will be selected in the next year or so for launch around the middle of the decade, and the ESA-NASA Mars Trace Gas Orbiter (MTGO) should leave Earth in 2016.

Then, if current budget projections hold, funding for new mission development will drop by approximately half around the middle of the decade.  The Flagship missions recommended by the Decadal Survey probably will not fit within that funding.  Steve Squyres said that with this funding level, the second half of the decade likely will see only New Frontiers and Discovery missions funded.

NASA and ESA had plans for a joint 2018 dual rover mission with NASA providing the launch, entry, and descent systems and a rover to cache samples for an eventual sample return.  ESA would provide its own rover to carry out sophisticated analysis of samples drilled from beneath the surface.  Unfortunately, adding the ESA rover would increase NASA's costs by approximately $1B, or a bit less than the cost of the ESA rover and instruments.  Today, even the cost of a NASA-only mission at $2.5B probably would be more than the projected budgets could afford with current budget projections

James Green, head of NASA's Planetary Science division, has said that NASA and ESA will spend the next several months  trying to craft a joint mission that fits within both agencies' budgets and meets both agencies' goals.  If that's possible, perhaps the resulting mission will be a single rover with ESA's instruments and NASA's sample caching hardware.  Whatever the solution, it will have to be designed to a cost cap.

Which brings us back to the figure I believe is so important.  The Science article pointed out that 50 years of planetary exploration have led to many "firsts": first flybys, first orbiters, first landers, first rovers for many worlds.  "But," and the article points out, "the next first is always more complicated than the last.  And greater complexity always means more expense."

The figure from the Survey's report shows the relationship between cost and mission complexity.  As mission complexity increases linearly, mission cost increases exponentially.  A mission with a relative complexity of 40% would cost approximately $100M.  Double that complexity to 80% and costs jump to almost $1B.

In a fixed budget, the key is to design to cost, with corresponding caps on the complexity of the mission. New missions extend the capabilities of previous missions in some new way: a sample return from a new region of the moon, or the first Venus lander with modern instruments, or the first mission to a Trojan asteroid.  Complexity and resulting costs are constrained by narrowly focusing the mission on only the core requirements.

New Frontiers and Discovery missions have always been planned with a design to cost philosophy with costs capped at ~$425M and ~$8650M, respectively (Principal Investigator costs for the spacecraft, instruments, and operations).  Flagship missions, on the other hand, traditionally were designed to meet a set of mission goals with the costs allowed to rise to meet those goals.

Flagship mission do not have to be designed that way.  Several researchers in the question and answer period pointed out that the original JEO proposal was for a cost capped ~$2+B mission.  NASA then asked for a more capable mission that would hit the sweet spot for maximizing science return, and the result was a $3+B mission, which the Survey estimated would actually cost $4.5B.

Cost capped missions are an intelligent way to fit more missions within a budget.  However, these missions must focus on narrower questions.  The initial cost-capped proposal that became the JEO concept, for example, had fewer capabilities to study the larger Jovian system.  Lower budgets and resulting cost capped missions will mean slower progress in understanding the solar system.

I learned one other key aspect about the Survey's recommendation this week.  In the press conference, Squyres said that the Survey concluded that the past almost twenty years focus on Mars had resulted in too little attention on the rest of the solar system.  With the exception of the relatively inexpensive MTGO mission, no missions are recommended for Mars unless they are part of a sample return sequence (which a 2018 rover mission would be).  Otherwise, the Survey believes that the goal should be a breadth of missions to many solar system locations and not return to Mars in the coming decade.

All in all, the future planetary program looks much different tonight than it did a month ago.  Since then, we've learned that future budgets are projected to be substantially lower, cost capped missions with tightly focused goals are likely to be the norm, and that Mars has lost its special status as the focus world.

With this post, barring news, I'll take a break from the Decadal Survey for a bit and look at some mission proposals.

I want to start this post by saying that all the details I'll present are certainly wrong.  However, I believe that the overall conclusion probably is approximately right.  And breaking with my tradition of having this blog focus on fact and not editorializing, this post is an editorial.

For the last several years, I've examined NASA's planetary program budget proposals to learn where it invests and how much its fully burdened costs for missions appears to be.  This is roughly the equivalent of looking through a business' annual statement to try to understand its operations and financial position (for example, to try to decide whether it might be a good stock investment).  There are always lots of hard concrete numbers, but you always have to make some assumptions.  Some of those turn out to be wrong, hopefully by a small amount but sometimes by a meaningful amount.  That's why the some of the assumptions embedded in the spreadsheet behind this post are almost certainly wrong, but the larger picture should be approximately right.

In this post, I'll summarize the key findings of my analysis.  For readers interested in the assumptions, I'll post those as a comment.  Since my detailed assumptions are likely to be wrong to some degree, I will give ballpark figures here.

Since the release of the Decadal Survey, I've gone back to re-examine the budget outlook presented in the FY12 NASA budget proposal.  The proposed budget for FY12 supports all missions in flight, in development, or committed.  Starting in FY13, however, budgets are projected to decline.  At the presentation releasing the Survey's recommendations, Steve Squyres (the Survey's chair) stated that given the out year budget projections, NASA would not be able to develop Flagship class missions in the coming decade.

Adding everything together, I estimate that missions in development and committed would cost somewhat more than $3B, leaving something more than $6B for additional missions.  Assuming two additional New Frontier and two additional Discovery missions, that leaves $1-1.5B  to apply to an additional mission.  To account for any costs I missed, I rounded down to $1B.  Depending on whether or not future budgets are increased to adjust for inflation, this remaining funding wedge might be lost to inflation.

This remaining approximately $1B could fund an additional Discovery mission.  However, this could be the seed money for a Flagship class mission -- presumably a 2018 Mars rover mission with ESA.  About another $1.5B in additional funding would be needed, or a total increase in the budget of about 15% over the coming decade.  (Maybe 20% to cover the simplifying assumptions I had to make.)

Steven Squyres emphasized in his presentation Monday night that all budgets beyond the current year are 'notional' and subject to change through the political process.  If we as the community that cares about planetary exploration want to see a Flagship mission from NASA in the coming decade, we need make the case to our politicians to increase the planetary budget by 15-20% above the plan presented in the FY12 budget.  We would not be asking for large budget increases.  Adding this money to the budget would result in a significantly smaller budget than if FY12 funding were to continue for the coming decade (the difference could fund a second Flagship mission).  The Planetary program still would share the pain of reducing Federal deficits.

I believe that the case for a Flagship mission in the coming decade is compelling.  I think this is a case we can and should make to the politicians.

Note: If any readers have better budget estimates than I used, contact me and I will post them.