Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 14
Scientific Assessment of NASA's SMEX-MIDEX Space Physics Mission Selections (Chapter 5) Scientific Assessment of NASA's SMEX-MIDEX Space Physics Mission Selections 5 Findings and Recommendations Findings 1. Both the most recently selected SMEX and MIDEX Explorers (TRACE and IMAGE, respectively) address high-priority scientific issues fully consistent with the current primary science goals of the solar and space physics discipline, as identified by the NRC Science Strategy report (SSB, 1995). Discussion: TRACE will observe the Sun with sufficient temporal and spatial resolution to allow, for the first time, detailed studies of the magnetic coupling of the corona to the photosphere. These observations have long been identified as essential to advance understanding of the sources of solar variability. IMAGE will carry out comprehensive global imaging of the Earth's REPORT MENU magnetosphere. Such measurements have been identified by the scientific NOTICE community as having the highest priority in advancing magnetospheric physics. MEMBERSHIP FOREWORD 2. Although the Explorers do an excellent job of focusing on specific EXECUTIVE SUMMARY scientific objectives, most of the broader top-priority objectives summarized in the CHAPTER 1 NRC Science Strategy report can only be accomplished with larger, more CHAPTER 2 scientifically capable missions. CHAPTER 3 CHAPTER 4 CHAPTER 5 Discussion: Certain challenges will require instrumentation beyond REFERENCES Explorer capabilities. These include very-high-resolution observations of small- APPENDIX scale structures (<100 km) on the solar surface, such as flux tubes, that may play a decisive role in solar activity; measurements of the composition of cosmic rays at very high energies; and tests for elements heavier than nickel. In situ observations of the solar wind acceleration region or of the heliospheric boundary and interstellar medium cannot be accomplished with Explorer launch vehicles. The required spacecraft technology is beyond what the Explorer program could support. Magnetospheric studies of Mercury for comparison with those of Earth are also beyond the scope of Explorers, both in their required launch capability and their need for comprehensive measurements. file:///C|/SSB_old_web/smexch5.html (1 of 5) [6/18/2004 1:44:01 PM]
OCR for page 14
Scientific Assessment of NASA's SMEX-MIDEX Space Physics Mission Selections (Chapter 5) Space physics thus has a critical need for an external line of Solar- Terrestrial Probes (such as TIMED), together with occasional use of larger Frontier Probes, to carry out its science program. The Explorer program can be successful only in such a context. 3. To succeed within their severe cost constraints, Explorer missions cannot afford instruments that require lengthy development or space qualification cycles. Therefore, the use of instruments and/or instrument subsystems that have been developed for previous missions is essential. The present funding cap on SMEX and MIDEX could well prove too restrictive for building scientifically first- rate missions without such instrument heritage. Lessons learned from the space physics Explorers demonstrate the importance of instrument and spacecraft heritage in meeting science goals while remaining within cost and schedule limits. Discussion: Instrument heritage derives both from R&A funding (e.g., Supporting Research and Technology [SR&T] and the suborbital program) and from development undertaken for major flight programs. The TRACE mission is a good example: It uses multilayer telescopes first developed in the laboratory by NASA SR&T funding and subsequently used in two rocket programs that obtained the first EUV normal-incidence solar images. TRACE has borrowed heavily from technology developed for the Extreme Imaging Telescope (EIT) and Michaelson-Doppler Interferometer (MDI) experiments on SOHO. Neither TRACE's cost cap nor its rapid schedule could have been met without this heritage. This cost-effective strategy could be jeopardized by the upcoming expected dearth of large flight programs. 4. The committees support NASA efforts to make the Explorer program more responsive to "missions of opportunity." However, they are concerned that relaxing current launch vehicle constraints on the Explorer program could attract suborbital and Shuttle-based missions that would previously have been funded under a different line. This could place additional strain on maintaining sufficient Explorer funding. Discussion: The key attribute of the Explorer program is that, given reliable launch vehicle options, it makes rapid access to space possible. This goal has consistently been the top recommendation of numerous science advisory panels to NASA. The agency is to be commended for addressing this challenge. The Office of Space Science (OSS) is now planning to modify the Explorer program so that it more closely resembles the Discovery program—for example, by including the Space Shuttle as an acceptable launch vehicle. Although the committees support the general concept of making the Explorer program more responsive to "missions of opportunity," less restrictive policies on launch vehicle options might have the unintended effect of reducing the funding available for Explorer missions. 5. The current operation and management styles of the SMEX program—including mutually beneficial cooperation between NASA and non- NASA participants, reduction of documentation, and flexibility in that class—are fostering opportunities for excellent, high-priority science. file:///C|/SSB_old_web/smexch5.html (2 of 5) [6/18/2004 1:44:01 PM]
OCR for page 14
Scientific Assessment of NASA's SMEX-MIDEX Space Physics Mission Selections (Chapter 5) Discussion: The small Explorer programs were widely praised by the investigator teams interviewed by the committees. The SAMPEX, FAST, and TRACE teams considered the SMEX program at GSFC to be well managed, with a high level of technical competence and a minimum of red tape. The SMEX program was a good example of a case where a "cheaper, faster, better" method has existed within the agency for some time (SSB, 1996). Because the MIDEX program has only just begun, the committee cannot comment on any distinctions between it and the SMEX program, but we strongly support the same approach. 6. The extremely low selection rate (2/50) among the large number of proposed Explorer missions results in much effort spent fruitlessly in proposal preparation. This extra work puts a significant burden on the research community and their industrial partners. Discussion: Such a low success rate is also a strong disincentive for the industry to participate in the proposal process. NASA's use of a multistep proposal process should help alleviate this problem. In this process, the initial mission concept proposal involves a smaller initial investment, with emphasis on the proposed science. After the first selection round, development funds are made available to help mould the selected concepts into full mission proposals (SSB, 1996). It is the committees' view that for efforts of MIDEX scope this approach will encourage creativity while minimizing the expense of the proposal process, in both human and economic terms. A second problem arising from the large number of proposed missions is the difficulty of finding expert peer reviewers without conflicts of interest. 7. As with many other flight missions, Explorer missions can often continue producing important scientific knowledge well after the scheduled mission termination if appropriate funding is available. Recommendations Based on the information from the briefings, subsequent deliberations, and findings, the committees recommend that NASA consider the following: 1. Establish a line of larger missions, such as Solar-Terrestrial Probes, because most of the broader, top-priority science objectives can only be accomplished with more capable missions. Explorer mission science could then be properly placed in the context of a coherent overall science program. This would include a balance of larger and smaller missions, suborbital projects, and R&A, all working synergistically to accomplish identified scientific objectives. For example, Explorer selections can materially contribute to the development of some of the technology needed for more ambitious missions. file:///C|/SSB_old_web/smexch5.html (3 of 5) [6/18/2004 1:44:01 PM]
OCR for page 14
Scientific Assessment of NASA's SMEX-MIDEX Space Physics Mission Selections (Chapter 5) 2. Adapt some of the management style and procedures associated with the SMEX program, as discussed in Finding No. 5 above, in other science programs. Recent spacecraft–PI mode space physics Explorers (such as SAMPEX and FAST) successfully demonstrate how high-priority science can be carried out in "faster, cheaper, better" ways. 3. Within NASA's R&A program, provide for some instrument development opportunities in addition to the suborbital program of rockets and balloons, because of the importance of instrument heritage to the success of many Explorer experiments. 4. With respect to Explorer program proposals, consult the advisory groups before the final-stage proposal review process for a broad range of inputs and suggestions regarding candidates for membership on its all-important technical proposal review panel. This process could have a better chance of finding expert peer reviewers free of conflicts of interest. file:///C|/SSB_old_web/smexch5.html (4 of 5) [6/18/2004 1:44:01 PM]