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An illustration of the proposed MAX-C Mars rover, identified as the top priority large, or “flagship”, mission in the latest planetary science decadal survey. (credit: NASA)

Tough decisions ahead for planetary exploration


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This is, in many respects, a golden era for planetary exploration. Last month NASA’s MESSENGER mission became the first spacecraft to go into orbit around Mercury; at almost the same time the New Horizons spacecraft was speeding past the orbit of Uranus, en route to its mid-2015 flyby of distant Pluto. Venerable spacecraft like Cassini orbiting Saturn and Opportunity roving across the Martian surface continue to make discoveries, and new spacecraft—Juno, GRAIL, and Curiosity—are slated for launch later this year. NASA has gone so far as to declare this the “Year of the Solar System”, albeit more of a Martian year, as its definition spans from last October though next August.

Yet, while the present and near-term future look bright, the longer-term outlook for NASA’s planetary sciences program is far more uncertain. A recent report identified the scientific community’s priorities for the next decade of planetary exploration, including missions to collect Mars samples for return to Earth and to orbit Jupiter’s icy moon Europa. But the high costs of some of those missions, coupled with tight budgets for years to come, could result in a far less ambitious future than many scientists desire.

No plan B for Mars

Last month the Space Studies Board of the National Research Council released the final report of the planetary sciences decadal survey, documenting the community’s priorities for future planetary science missions from 2013 through 2022. The report, similar to those prepared in astronomy, earth science, and other disciplines, provides guidance to NASA on what missions scientists believe the agency should be funding as part of its planetary science program.

One major difference of this decadal survey was an emphasis on affordability, specifically, selecting programs that would fit into the long-term projected budget profile for NASA’s planetary science program.

The report was rolled out at the Lunar and Planetary Sciences Conference (LPSC) in Houston by the study’s chair, Steve Squyres, the Cornell University planetary scientist best known for his role as the principal investigator on the Mars Exploration Rovers program. In his presentation at LPSC, he talked a packed ballroom of planetary scientists, and others watching via webcast, through the report.

“All of the priorities, and all of the recommendations, were guided as strongly as we could be guided by community inputs,” he said, referring to the long process of working group meetings and white paper submissions. Working groups in several areas—Mars, other inner planets, giant planets, and so on—developed priorities within their own disciplines that were then synthesized by the steering committee. He said the final priorities were made by “very strong consensus”, often by a unanimous vote of the 16-member steering committee.

One major difference between this survey and previous decadal surveys, Squyres said, was an emphasis on affordability, specifically, selecting programs that would fit into the long-term projected budget profile for NASA’s planetary science program. “What that did was make it necessary for us to put attention on not just the science, but also on the costs of the science,” he said. That would have major implications for their recommendations.

The report recommended a balanced approach, both in classes of missions and planetary destinations, in its final report. It recommended NASA continue its Discovery class of smaller planetary science missions and the New Frontiers class of medium-sized missions, although leaving the selection of specific missions to future competitions. It also called for gradually increasing research and analysis (R&A) funding as well as technology development for future planetary missions.

For large “flagship” missions (defined in the report as those costing more than $900 million) the decadal survey did make specific recommendations. Its top priority is the Mars Astrobiology Explorer-Cacher (MAX-C), a rover that would collect and cache samples in the first of a three-phase sample return mission concept. (A second mission would be a lander that retrieves the cached samples and launches them into Martian orbit; the final phase would feature an orbiter that collects the samples in orbit and returns them to Earth.)

The second highest priority flagship mission is the Jupiter Europa Orbiter (JEO), similar to the Europa orbiter concept identified as the top flagship mission in the previous decadal survey. It, in turn, is followed by a Uranus orbiter and probe mission, and then an orbiter to Saturn’s icy moon Enceladus and a Venus mission featuring a combination of atmosphere probes and a balloon.

“There’s no ‘Plan B’. There’s no alternate plan for Mars exploration recommended,” Squyres said. “If you can’t do MAX-C for $2.5 billion, there are other high-priority flagship missions that take precedence over something else you might do at Mars.”

Cost, though, plays a major factor in which—if any—of those missions might eventually fly. Unlike previous decadal surveys, this study subjected proposed mission concepts to what it called an independent cost and technical evaluation (CATE), performed by the Aerospace Corporation. Those evaluations often provided a very different—and higher—estimate of the costs of those missions than those provided by the mission’s proponents. The CATE for MAX-C estimated its cost at $3.5 billion, compared to the project’s own estimate of $2.2 billion. JEO had its cost go from $3.4 billion to $4.7 billion. (All costs in the report are expressed in fiscal year 2015 dollars.)

“The result is some sticker shock,” said Ralph McNutt of Johns Hopkins University Applied Physics Lab, a member of the steering committee, at a “town hall” meeting about the decadal survey March 25th at the University of Maryland in College Park, one of several taking place around the country in the weeks following the report’s release. He added that he wasn’t as shocked as some, given his experience with missions like MESSENGER, where he serves as project scientist. “The real issue was to get some realism into the system.”

Those revised cost estimates led the survey to include some caveats into its flagship mission recommendations. MAX-C is the top priority flagship mission only if the cost of the mission can be reduced to about $2.5 billion by descoping the mission. Similarly, JEO is the second priority only if its cost can be significantly reduced through descoping, and by also increasing NASA’s overall planetary budget.

This has particularly significant implications for Mars exploration in particular: the study recommends that if MAX-C can’t fit within that $2.5-billion cost cap, it should be “deferred until a subsequent decade or cancelled outright,” with nothing taking its place. “There’s no ‘Plan B’. There’s no alternate plan for Mars exploration recommended,” Squyres said, adding this was the recommendation of the Mars subcommittee. “If you can’t do MAX-C for $2.5 billion, there are other high-priority flagship missions that take precedence over something else you might do at Mars.”

Dealing with a constricting budget

The decadal survey worked to fit their mission proposals within a budget profile provided by NASA, based on the fiscal year 2011 budget request. That request called for gradually increasing budgets for planetary science, from $1.49 billion in 2011 to $1.65 billion by fiscal year 2015; the study assumed growth would continue at the rate of inflation through 2022.

A few weeks before the report’s release, though, the planetary science community got another shock when the White House released its fiscal year 2012 budget proposal. While projections for the “outyears” beyond 2012 are considered notional, they show the planetary science budget decreasing: from $1.54 billion in 2012 to less than $1.26 billion by 2016. That upsets all the assumptions and projections used in study.

The 2012 budget proposal, Squyres said, “would mean the end of flagship-class science at NASA in the planetary program.”

In particular, it would likely mean that none of the proposed flagship missions in the decadal survey would fly. The survey created a set of “decision rules” should the budget be smaller than their projections based on the 2011 budget proposal. Under those rules, the first step would be to descope or delay flagship missions; only if those measures aren’t enough should NASA consider changes to the Discovery and New Frontiers program while preserving R&A and technology development funding.

“If that budget were actually implemented,” Squyres said of the 2012 budget proposal, “it would mean the end of flagship-class science at NASA in the planetary program.”

“What’s on the table right now for the outyears is not very good,” McNutt said. However, he reminded attendees of the Maryland town hall meeting that the planetary science program at NASA has been in dire straits in the past, such as in the early 1990s, but later improved. “This might turn around, or might not turn around. In the meantime, this is what’s on the table.”

Further complicating those decisions is that MAX-C is part of the joint ESA/NASA ExoMars exploration program. Under that plan, MAX-C would be launched in 2018 along with an ESA rover, so any changes to MAX-C would have to be discussed and negotiated with the Europeans.

In a Space Transportation Association speech on Capitol Hill on March 25th, NASA administrator Charles Bolden said discussions were already underway with ESA on how to descope that 2018 mission to bring the cost down. “We are having to take things off the table,” he said. “Why do we need two rovers, for example, when one will do?”

“We will not put humans on Mars without several sample returns,” Green said.

At the Maryland town hall meeting, some wondered why MAX-C got top priority as a flagship mission when it is the first step in the three-phase sample return mission: was it wise to commit the agency to many billions of dollars more in follow-on missions in the years following MAX-C given the budget environment? McNutt said this could be seen as a “gutsy strategy”, but it reflected the priorities of the planetary science community, in particular Mars scientists who believe it’s time to move on to a sample return mission.

Jim Green, director of the planetary science division at NASA headquarters, defended the decision to press ahead with a Mars sample return mission, noting that it is likely to be an international venture given the cost, and also essential to future human exploration. “We will not put humans on Mars without several sample returns,” he said at the town hall meeting. “If not now, when? If we can’t get the nation or the world excited about that now, when?”

Squyres and others sought to portray the proposed budget not as a fait accompli, but instead something that could be changed if the scientific community got behind the decadal survey and lobbied Congress for the funding necessary to carry out those missions. Some note that while planetary science sees decreased funding in the future in the budget proposal, Earth science gets an increase, in part because that community has rallied to support missions identified in its own decadal survey a few years ago.

“Those of us who care about planetary exploration have not just the right but I believe the obligation to speak to our congressional representatives about the planetary budget and to make it very clear what program we would like to see,” Squyres told the LPSC audience last month. He added that he briefed staffers on congressional appropriations committees about the report shortly before its release. “One message that I got from them loud and clear is that they do support planetary exploration and see this as one of the great things this nation can do,” he said. “But the question that they asked me is, ‘where is your community?’”

That sentiment was echoed by McNutt at the Maryland town hall meeting, who called the decadal survey’s report “the best job you could do” to create a consensus report. “It is vitally important,” he said, “that the community get together and support this document as the going forward plan.”


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