fulfilled by Scouts. The SSE decadal survey was highly supportive of the initiation and continuation of the Mars Scout line, and so NASA is to be commended for the inclusion of two Scout missions in the period under consideration—i.e., Phoenix in 2007 and an as-yet unselected mission in 2011. Indeed, the inclusion of two missions is in accord with the decadal survey’s recommendation that a Scout be included at every other Mars launch opportunity.

2016 Mission Selection

Choosing between the alternatives for the 2016 opportunity will depend on the results of the Mars Reconnaissance Orbiter and the initial results from the Mars Science Laboratory. As stated above, the committee is concerned that there may not be sufficient time for analysis of MSL data before a decision must be made on the 2016 opportunity. Indeed, the document Mars Exploration Strategy 2007-2016 comments that the “response time for missions to investigate findings from prior missions [is] typically 6 to 7 years.”3 Thus, by the architecture’s own admission, it is far from clear how a mission launching in 20164 can be influenced by the results from MSL, which will not reach Mars until the middle months of 2010.5 NASA needs to articulate explicitly a strategy to address the short lead time between science results obtained from MSL and selection of the mission to fly in 2016. Of equal or greater concern is the absence from the architectures of any criteria for distinguishing between the various options for launch in 2016. NASA needs to clarify how trade-offs between mission costs versus science will be made for the various launch opportunities to justify the rationale behind the proposed sequence of specific missions and the exclusion of others.

Summary

The committee cannot definitively say whether or not the revised Mars architecture addresses the goals of NASA’s Mars Exploration Program because the architecture lacks sufficient detail with respect to science and cost to allow a complete evaluation. The various mission options are, as already stated above, not fully defined, and the strategic approach to, and selection criteria to distinguish between, various mission options is lacking.

OPTIMIZING THE SCIENCE RETURN

Does the Mars architecture optimize the science return, given the current fiscal posture of the program? The anticipated budget for NASA’s Mars Exploration Program over the next 5 years is about $3 billion less than expected as recently as 1 year ago. This reduction is not unique to the Mars program. The combined effect of recent delays, descopings, deferments, and deletions of other NASA science programs led a Space Studies Board committee to conclude that the “program proposed for space and Earth sciences is not robust; it is not properly balanced to support a healthy mix of small, medium, and large missions and an underlying foundation of scientific research and advanced technology projects; and it is neither sustainable nor capable of making adequate progress toward the goals that were recommended in the National Research Council’s decadal surveys.”6 Nevertheless, the Mars Exploration Program’s current budget still amounts to some $600 million per year, and so a mission costing as much as $1 billion could, in principle, be flown at every Mars launch opportunity. On the other hand, the near-to mid-term expectation is for flat budgets, and so inflation will eat away at the program’s buying power over time. Yet, in the near term at least, the resources available for Mars exploration are still remarkably healthy. If the architecture is regarded purely as a sequence of near-term missions, then NASA is to be congratulated for designing missions that will almost certainly provide a science return at least commensurate with what the Mars program has achieved over the last 5 years.

The Mars Exploration Program’s prospects over the longer term are far from clear. The program’s resilience in the face of major upsets is an issue of concern to some observers. The cost of MSL has grown significantly in the past few years. What if its costs continue to grow? What happens if its new landing system fails and MSL is lost? The key to a robust program is a mix of orbiters and landers, a mix of large and small missions, and a mix of strategic and PI-led missions. Problems are likely to arise when the coupling between missions at adjacent launch



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