23

The Future

A decadal survey, by definition, looks 10 years ahead.¹ Predicting the future is fraught with challenges. Moreover, many of the concepts and recommendations contained in the preceding chapters may not be implemented or their consequences known until multiple decades from now.

The coming years will witness events that were unforeseen when this report was drafted. New scientific discoveries, technical developments, and budgetary booms or busts are inevitable and all will impact the implementation of the recommendations in this report. Thus, the survey report and the policy ecosystem within which it exists is most effective if it can accommodate the inevitability of change. Therefore, the survey committee has endeavored, via the two representative programs and the decision rules in Chapter 22, to provide some guidance as to how budgetary changes in the near-to-mid-term might be accommodated. Longer term resilience is beyond the purview of the survey committee but is provided by via two mechanisms, continuing oversight of the implementation of decadal surveys and the midterm review process.

CONTINUING OVERSIGHT

Vision and Voyages noted the following: 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? . . . 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 (NRC 2011).

In response to this call for strategic guidance, the National Academies established the Committee on Astrobiology and Planetary Science (CAPS) in 2012 and gave it the specific tasks to provide continuing oversight of the implementation of the decadal survey and to act as the organizing committee for future surveys and for other relevant reports. In 2016, CAPS was re-chartered to give it the ability to draft short reports on topical issues of relevance to the implementation of the prior decadal survey and related reports. At NASA’s request, CAPS completed four such reports in the period 2017–2020 on topics as diverse as how the agency could best prepare for this decadal survey (NASEM 2017), the Lunar Exploration and Development Program (NASEM 2019a,b), and options for the next New Frontiers announcement of opportunity (NASEM 2020).

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¹ A glossary of acronyms and technical terms can be found in Appendix F.

Finding: The Committee on Astrobiology and Planetary Science is succeeding in its role of monitoring the implementation of the recommendations in the most recent relevant decadal survey as evidenced by the steady stream of requests from NASA for the committee’s input.

THE MIDTERM REVIEW

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.” The primary reason cited in the Act for undertaking such reviews was to evaluate the progress or lack of progress of the agency at meeting the goals of the decadal surveys. Such information could then be used by legislators to improve NASA’s responsiveness to the survey recommendations. Vision and Voyages noted that in addition to assessing NASA’s progress toward implementing decadal goals, such midterm reviews could also be used to gauge the degree to which scientific understanding has advanced since release of the last survey. Indeed, the most recent midterm review committee was tasked to describe “the most significant scientific discoveries, technical advances, and relevant programmatic changes in planetary sciences over the years since the publication of the planetary decadal survey (Vision and Voyages)” (NASEM 2018).

A question frequently asked is whether a 10-year planning horizon is too long or too short. Arguments for a decade-plus horizon often note that the timescale for planning, building, and launching even small-class spacecraft missions is approaching a decade. Large-class missions often require multi-decade timescales from inception to first results, and even longer if necessary technology development activities are considered. However, given the rate of scientific and technical development and the vagaries of the annual budget cycle, any attempt to plan for several decades hence seems doomed to failure. Moreover, given the substantial effort required of a significant fraction of the community to undertake a decadal survey, repeating the exercise on a sub-decade timescale would meet with many obstacles. Therefore, efforts to turn the midterm review into a semi-decadal survey are misguided. Indeed, one of the best practices identified in the 2015 review of the decadal survey process (NASEM 2015) was that, “Midterm assessment reports are most useful when they engage and inform the broad community by providing a progress report on implementing the decadal program, together with sufficient context to understand the rationale behind the program’s current implementation strategy.”

Finding: The survey committee echoes the sentiment expressed in the Vision and Voyages that a 10-year assessment and planning timescale and a 5-yearly review cycle is appropriate at the present time. Moreover, the midterm review is most effective if it reinforces the prior decadal survey and is not used to reprioritize or otherwise make significant modifications to the latter’s key recommendations.

PREPARING FOR THE NEXT PLANETARY DECADAL SURVEY

All three planetary science decadal surveys conducted to date have been asked to identify and prioritize the highest priority large- and medium-class spacecraft missions to be initiated in the next 10 years. The first planetary decadal was forced to rely on prior mission studies of variable fidelity and to devise its own concepts. The lack of technical realism embodied in some of its priority mission recommendations became apparent soon after the report’s release.

The second decadal survey fared better because it could draw upon several detailed mission studies undertaken by NASA and was also able to commission some medium-fidelity mission studies. The latter were performed over a relatively short timescale while the survey was under way. Formulating and studying 25 mission concepts in parallel with the drafting of the decadal survey caused considerable stress to the survey’s schedule and on the workload of those members participating in the studies. This less than ideal situation prompted Vision and Voyages to comment that 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.”

As a result, that survey recommended 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.” This call was

reiterated by CAPS and the midterm review (NASEM 2017, 2018), and NASA eventually initiated the predecadal planetary mission concept study (PMCS) process. Eleven concepts were studied via the PMCS mechanism (see Appendix C) and were completed in 2020.

The availability of the PMCS reports greatly helped the survey committee formulate this report. However, the 11 PMCS concepts did not adequately represent the full scope of scientifically interesting and technically feasible projects that might be initiated in the coming decade. Fortunately, NASA was able to provide sufficient resources for the survey committee to commission 10 additional studies (nine addressing science and one addressing planetary defense goals).

Finding: The predecadal mission concept study process represented an important innovation in NASA’s support of the decadal process and greatly assisted the work of the survey committee in the formulation of this report.

While helpful, the PMCS process was not without its faults. If the process or something similar is used to prepare for future decadal surveys, the following changes are suggested:

• Consider forming an appropriately constituted group representing the scientific community to recommend a strategic set of mission studies needed to address priority science questions prior to an open call for such studies. This list would not be restrictive but could help ensure that needed studies are performed;
• Increase the number of concepts studied beyond 11 to relieve the decadal survey of some of the burden of conducting its own studies;
• Discourage the formulation of overelaborate concepts incorporating comprehensive instrument complements and/or multiple interacting spacecraft;
• Encourage the inclusion of multiple descope options;
• Disincentivize reliance on new launch and/or power systems whose availability might not be consistent with a realistic mission timeline;
• Avoid reliance on a single potential launch vehicle; and
• Consider multiple launch opportunities in the decade(s) beyond that covered by the survey.

REFERENCES