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Assessment of Mission Size Trade-offs for NASA’s Earth and Space Science Missions APPENDIXES

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Assessment of Mission Size Trade-offs for NASA’s Earth and Space Science Missions A Letter of Request from NASA to the Space Studies Board

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Assessment of Mission Size Trade-offs for NASA’s Earth and Space Science Missions National Aeronautics and Space Administration Headquarters Washington, DC 20546-0001 APR 22 1999 Reply to Attn of: SR Professor Claude Canizares Chair, Space Studies Board National Academy of Sciences 2101 Constitution Avenue, NW Washington, DC 20418 Dear Professor Canizares: Both the Earth Science Enterprise and the Space Science Enterprise have, during the past few years, created near-and longer-term goals for their scientific programs, as well as missions to accomplish those research goals. The Space Studies Board (SSB), as well as other boards and task groups, have had a major role in shaping and reviewing those science plans and planned missions. We believe that the planned missions in each of our two disciplines consist of balanced sets of small, medium, and large missions, tailored to the range of science questions to be addressed, and as dictated by the physics of each observation to be conducted. Recently, there has been much emphasis on selecting, building, and launching “smaller, faster, cheaper, better” missions. Sometimes this emphasis created the impression that NASA has completely abandoned the mediumand larger missions which we have traditionally emphasized. Congress has directed NASA to: “. . contract with the National Research Council (NRC) for a study across all space science and Earth science disciplines to identify missions that cannot be accomplished within the parameters imposed by the smaller, faster, cheaper, better regime. The [study] report should focus on the next 15 years, and attempt to quantify the level of funding per project that would be required to meet the specified scientific goals. The report also should identify any criteria

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Assessment of Mission Size Trade-offs for NASA’s Earth and Space Science Missions and methods that could be used to measure whether the science accomplished using small satellites is better than that accomplished with larger, more complex spacecraft. The report is to be submitted to the Committee no later than September 30, 1999.” The purpose of this letter is to request that the SSB conduct such a study. We are addressing the SSB since it is the NRC entity with the longest connection to the science interests of both Earth and space science disciplines, and assume that other entities will be involved as appropriate. The level of funding for each project in the next 15 years will depend on its precise science objectives and implementation. Since mission planning for the latter part of the 15-year interval is currently underway in both the Office of Space Science and the Office of Earth Science, and since important elements of these offices’ programs will be accomplished through competitive selections in the community-based Explorer, Discovery, and Earth System Science Pathfinder lines, a complete allocation of science objectives to particular missions cannot be made at this time. For the later part of the 15-year period, your assessment may address generic mission ideas presented in the strategic plans. For the purposes of this study, we request that you consider three broad mission categories: Small missions with a total cost (including 1aunch, operations, and science analysis) of less than $150M; medium missions with total costs up to $350M; and large missions, including strategic missions and observatories, with a total cost (including launch, operations, and science analysis) of more than $350M. We recognize that the completion date of September 1999 is likely to pose a difficult challenge, and request your views about the earliest feasible time scale for completion of a study addressing the following specific questions: What are the general criteria for assessing strengths and limitations of small, medium, and large missions in terms of scientific productivity, including quality and amount of science value returned, responsiveness to

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Assessment of Mission Size Trade-offs for NASA’s Earth and Space Science Missions evolving opportunities, ability to take advantage of technological progress, and other factors? Within the near term, which science goals as provided in our strategic plans will require the use of medium and large missions, in terms of the definitions above and the strengths and limitations in (1) above? Although, the scientific goals and our mission plans are evolving, fairly complete recent summaries can be found at, and at We look forward to receiving your proposal, including study costs and estimated completion date. If you require further information on our current plans, and to discuss study charter and implementation, please work with Dr. Jack Kaye, Director, Research Division, and Ms. Anngienetta Johnson, Director, Program Planning and Development in the Office of Earth Science, and Dr. Guenter Riegler, Director, Research Division, Office of Space Science. For contractual matters, please contact Ms. Dolores Holland at 202/358-0834. Sincerely, Ghassem R. Asrar Associate Administrator for Earth Science Edward J. Weiler Associate Administrator for Space Science cc: NRC/Mr. J. Alexander