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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.
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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.
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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.
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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.
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