Although this report establishes priorities for planetary science for the next decade, some of the missions it describes will not be launched until the mid-to-late 2020s. Others—e.g., the Uranus Orbiter and Probe—will take many years to reach their destinations. The Mars Astrobiology Explorer-Cacher mission will set NASA on a path that will only be completed when future missions are sent to retrieve the samples from Mars in subsequent decades. The committee’s recommended technology development program will enable many missions both in the near and distant future. This report will therefore have a legacy that goes well beyond the current decade.
Events inevitably will occur in the coming decade that this study cannot foresee. New scientific discoveries will be made, reshaping priorities for subsequent decadal surveys. The technology program that this report recommends will enable a broad range of future missions, including ones that the committee has not considered in any detail. A look backward shows that things have changed since the 2003 decadal survey, including significant changes to the political and budgetary environment in which NASA and NSF operate. The recommendations of this report have been made with the realization that future change is inevitable; the responses to this report must take into account the inevitability of change.
Section 301(a) of the NASA Authorization Act of 2005 directed NASA to have “[t]he performance of each division in the Science directorate … reviewed and assessed by the National Academy of Sciences at 5-year intervals.” In 2006 NASA asked for an assessment of the agency’s Planetary Sciences Division.1 The planetary exploration midterm assessment produced the report Grading NASA’s Solar System Exploration Program: A Midterm Report in 2008.2
The authorization act calling for these midterm assessments cited several reasons for conducting the midterms. The primary one was to evaluate the progress or lack of progress of the agency at meeting the goals of the decadal surveys. This information could be used to identify management or budget changes that might be necessary to improve responsiveness to the surveys.
It is possible that Congress will continue to call for midterm assessments of the decadal surveys. A midterm assessment could evaluate NASA’s accomplishments of the goals of the decadal survey to date, and assess the degree to which scientific knowledge and understanding have advanced since the decadal survey.
The long timescales of spacecraft missions make planning on a decadal timescale appropriate, and the effort required once every 10 years for the science community to produce a decadal survey is substantial. If a midterm assessment is carried out, it must be carefully constructed to reinforce the decadal survey process, while still taking into account any new discoveries or other changes that have taken place.
There are other things that NASA and the planetary science community can do to prepare for the next decadal survey. Two of the most important are as follows:
• Monitoring the implementation of the survey—Agency budgets wax and wane, new scientific discoveries are made, and new technologies come to the fore. Change, both good and bad, has an influence on the planetary science agenda and will affect the implementation of the recommendations in this report. A decadal survey should not be blindly followed if external circumstances dictate that a change in strategy is needed. But who decides if change warrants a deviation from a decadal plan? The potential candidates—internal agency advisory committees, community based “analysis groups,” and NRC committees—are not currently chartered to play such a role. A group specifically tasked to monitor and assess progress toward decadal goals is essential. Such a group should be able to provide the necessary strategic guidance needed to achieve the decadal science goals in a timely manner and consistent with the survey recommendations.
• Mission studies—This decadal survey commissioned numerous mission studies that were carried out over a relatively short period of time and then subjected to cost and technical evaluations. A more effective method would be for NASA to sponsor studies for potential flagship and New Frontiers missions that capture the broadest possible science questions as well as reduce the time pressure on the decadal survey itself. The committee therefore recommends that NASA sponsor community-driven, peer-reviewed mission studies in the years leading up to the next decadal survey, using a common template for the study reports.
1. In 2006 NASA also asked the National Research Council to conduct such an assessment for the agency’s Astrophysics Division. In 2007 NASA asked the NRC for an assessment of the agency’s Heliophysics Division. The NRC is currently undertaking an assessment of the Earth Sciences Division.
2. National Research Council. 2008. Grading NASA’s Solar System Exploration Program: A Midterm Report. The National Academies Press, Washington, D.C.