In this chapter, the committee provides a summary of observations and lessons learned during its assessment of the NASA Earth science program and NASA’s progress in implementation of the 2007 Earth science and applications from space decadal survey.1 The committee provides these observations in the belief that they will prove useful in optimizing the science value of the Earth science program going forward. It also believes that these observations will be useful to future advisory committees that may be charged with developing the next major iteration of the decadal survey. However, the committee also recognizes that advances in Earth science and in technology, and/or changes in U.S. government policy or funding related to Earth science that cannot be foreseen, may preclude or negate consideration of some of its guidance.
Although changes or advances in the field might necessitate alterations to the Earth science program over time, the committee believes that any future study aimed at designing a new set of missions for the Earth science program should retain a long-term focus on the program priorities that underlie the current mission queue, even as it recommends new avenues for investment based on scientific and technological progress over the time period established by such a study (e.g., a decade). Future mission queues drawing from those provided in the decadal survey would likely best serve both the science community and applications end users by leveraging progress already made on missions in implementation or formulation and by continuing the legacy of what the first decadal survey of Earth science and applications from space, the 2007 decadal survey, set out to accomplish. Retaining a fixed, predictable mission queue is essential to preventing devolution into mission- or discipline-specific advocacy groups that can seriously damage the community-based priorities established by the survey and undermine the community consensus critical to any major programmatic review. With a fixed and predictable queue, communities with missions ap-
1National Research Council, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, The National Academies Press, Washington, D.C., 2007.
pearing later in the queue have some assurance that the mission will indeed be implemented and remain an integral part of Earth system science. Retention of and investment in such long-term priorities are thus crucial to enabling a balanced program and reaffirming NASA’s commitment to the entire suite of missions. To maintain the survey’s long-term vision for a balanced Earth system science and applications program, this fixed and predictable queue would be complemented by a steady stream of opportunities to facilitate the demonstration of innovative ideas and higher-risk technologies to provide a mechanism to support new discoveries and add an element of flexibility to the program.
The science priorities identified by the 2007 decadal survey have provided the foundation for advancing Earth system science with the recommended set of missions. In its assessment of NASA’s implementation of the survey, the committee discussed at length whether specific mission recommendations were a necessary part of science priority setting, and presenters to the committee over the course of the study did not always favor one approach over the other. Finding balance between prioritizing science objectives and constraining how those objectives are accomplished will no doubt be one of the major tasks for any future study aimed at creating a new mission queue and set of scientific objectives for NASA’s Earth science program. However, the committee concluded that establishing at least notional mission concepts that can accomplish the prioritized objectives is essential to ensuring that the priorities are indeed reasonable and achievable. Similarly, development of mission recommendations allows for a sense of scope and scale to be conveyed that is lacking from a simple listing of target areas for investment. The committee thought that establishing science priorities devoid of implementation recommendations could easily be misconstrued as endorsements for one discipline over another.
In the course of this midterm assessment of the 2007 decadal survey’s implementation, it became apparent to the committee that large cost growth in missions early in the queue presents a real danger to programmatic balance. It also tends to encourage commensurate growth in later missions, effectively stretching program implementation and pushing later missions inexorably toward future dates, thus discouraging entire segments of the Earth science community and threatening the Earth system science goals set forth by the survey.
However, future community prioritization exercises should avoid pursuing the path of ever-more-detailed cost estimates at the expense of attention to scientific priority setting—the latter being the primary goal of any such review. Even in a cost-constrained environment, some mission cost growth is likely, if not inevitable. The committee does not discourage rigorous cost estimation at the appropriate time during formulation, a practice that serves an important purpose—but equally important is setting up clear budgetary decision rules that will help decision makers adjust to a changing fiscal environment and maintain the overall goals laid out in the vision put forth in any suggested future program.2To supplement such budgetary decision rules, consideration should be given to the use of mission cost caps that would help prevent
2Consideration should be given to establishing relative investment levels for recommended missions rather than leaving the cost of recommended missions unconstrained. Individual missions, then, would not claim enduring priority over other missions regardless of ultimate implementation cost, thus facilitating maintenance of programmatic balance across Earth system science. NASA would set an appropriate cost cap once more detailed implementation studies, guided by the recommended investment level, have been completed. The 2007 decadal survey attempted to convey a sense of scale through its rough cost estimates, but it stopped short of establishing or recommending a cost cap approach.
science-requirements creep from being the primary driver in mission design and development, a situation that has led to near-catastrophic cost estimate growth with some of the current decadal survey missions.3
Although the 2007 decadal survey presented a number of strategies and rules to help alleviate potential budgetary pressures placed on the Earth science program and implementation of the survey missions (Appendix B), more proscriptive decision rules and /or an explicit recommendation to implement missions via a cost-constrained approach might have been more useful in giving program managers a clearer idea of how to proceed to accomplish science objectives and maintain a healthy and balanced portfolio in the face of program adversity. The committee also recognizes, however, that the NASA Earth science program must retain its flexibility to deal with the many shorter-term challenges and opportunities that arise over the course of a decade while community priorities are being implemented.
As NASA proceeds with implementation of the current decadal survey mission portfolio, there are actions that the agency can perform now to prepare for future major programmatic reviews and priority-setting exercises. The committee suggests that NASA work proactively to identify the potential for value-added international partnerships ahead of, and separately from, future programmatic reviews. Similarly, opportunities to satisfy science objectives in non-traditional ways (e.g., constellation approaches, hosted payloads, suborbital campaigns) should be given due consideration. Such early preparatory work would help future committees and/or decision makers more easily identify synergies and potential cost savings as they craft a new mission queue.
3The CLARREO mission, for example, was recommended as a small mission and had grown to a large mission before being tabled for further formulation work prior to implementation.