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Assessment of Solar System Exploration Programs 1991 (Chapter 9)
Assessment of Solar System Exploration Programs
1991
9
General Programmatic Issues
In this section we address several general issues that have a substantial
impact on NASA's planetary science programs.
PLANETARY FLIGHT PROGRAMS
Small Missions Program for Planetary Exploration
NASA's Solar System Exploration Division is developing a new initiative,
named the Discovery Program, for carrying out small, low-cost spacecraft
missions. Potential aspects of this program would cover a triad of "small
REPORT MENU
missions," "mission partnerships," and "mission participations." The small
NOTICE
missions portion of the program would consist of simple, small spacecraft costing
MEMBERSHIP
under $100 million. Mission partnerships could include joint missions or
FOREWORD
collaboration on building instruments, whether between government agencies in
SUMMARY
the U.S. or with other countries. Mission participations might involve the provision
CHAPTER 1
of instruments, of spacecraft subassemblies, and of self-contained mission
CHAPTER 2
components such as surface probes.
CHAPTER 3
CHAPTER 4
CHAPTER 5 This program has similarities to the Explorer Program in the Astrophysics
CHAPTER 6 and Solar and Space Physics divisions, and to the new Earth Probes line in the
CHAPTER 7 Earth Science and Applications Division. We note here some of the reasons for
CHAPTER 8 the past successes of the Explorer Programs as stated in three Space Science
CHAPTER 9 Board reports: Strategy for Earth Explorers in Global Earth Sciences (SSB,
REFERENCES
1988c), The Explorer Program for Astronomy and Astrophysics (SSB, 1986a),
and A Strategy for the Explorer Program for Solar and Space Physics (SSB,
1984). These reports found that such small mission programs promote frequent
access to space; support specific, well-defined scientific objectives; enhance
programmatic flexibility because of their small size and shorter lead-time
requirements than larger missions; provide data not obtainable from the ground,
yet not acquired in larger missions; provide opportunities for international
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Assessment of Solar System Exploration Programs 1991 (Chapter 9)
cooperation; and augment training for science and engineering students at
universities.
A Discovery Program could bring many of these advantages to the
planetary exploration program. The mission and program structure should be
such that no single element absorbs the program resources for more than two
years. The selection process ought to be structured so that a large investment in
engineering design is not required. The data from the missions should be
delivered to scientific archives in a timely manner, and adequate funding for data
analysis and related theoretical modeling must be available.
While the desire to provide additional diversity and breadth to the
planetary program is worthy in itself, particularly with regard to program balance,
the Discovery Program needs to carefully choose objectives and goals that are
worthwhile, largely unattainable by other means, and within its resources. A
major requirement of proper implementation is an adequate and steady source of
funding directed at carefully chosen scientific objectives. Discovery missions to
near-Earth asteroids and to Pluto have been considered. The committee supports
further investigation of these and other missions for the Discovery Program.
Reserves for Flight Missions
The provision of adequate reserves for flight missions is vital to the
delivery of instruments and spacecraft systems on schedule and within cost. The
lack of adequate reserves on a year-by-year basis can lead to more—not
less—cost growth, as there is a tendency to push problems into later years when
remedies may be more costly and more drastic. The scientific integrity of a
mission may be threatened by cost-saving measures, or funding may be
transferred from other activities such as R&A programs, producing unanticipated
and detrimental effects on program science. In extreme cases, instruments may
be sacrificed, not because they have low priority, but simply because their
funding for a single year matches a mission deficit for that year.
To avoid these problems, missions need to be planned carefully and carry
adequate reserves for each year. When year-by-year caps are imposed, whether
by NASA or by Congress, the mission budgets must reflect accurately the
schedule of work to be done at the instrument and spacecraft assembly level,
and must include adequate reserves.
RESEARCH AND ANALYSIS PROGRAMS
The scientific achievements of planetary exploration are not limited to the
time of the nominal mission. Significant advances in understanding occur during
extended mission phases, post-mission data and analysis programs, thematic
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Assessment of Solar System Exploration Programs 1991 (Chapter 9)
study programs, and basic R&A. Such programs are essential for fully realizing
the scientific potential of each mission and for establishing critical objectives for
future exploration.
Results from the Mariner 10, Viking, and Voyager missions have all
underscored the importance of extended mission phases. Follow-on encounters
of Mercury by Mariner 10 acquired multiple data sets of the near-Mercury
environment. The extended Viking mission allowed high-resolution imaging of the
surface that profoundly affected our understanding of surface processes. Without
the extended Voyager mission, Uranus and Neptune would remain unexplored.
Magellan's nominal mission will not provide gravity data for Venus, fill in gaps left
by solar conjunction, or allow for a search of short-term changes on the planet's
surface. Therefore, the committee strongly recommends approval for the
extended mission for Magellan.
Post-mission data analysis programs not only capitalize on unique and
ephemeral expertise gathered during the mission, but also maximize the overall
scientific return by involving new perspectives, techniques, and approaches from
the science community at large. In general, COMPLEX expresses its support for
the development within the Solar System Exploration Division of an ongoing
sequence of data analysis programs, each of approximately three years' duration
and focused on the analysis of data from specific missions. These programs
serve to broaden the involvement of the planetary science community at an early
date and also provide opportunities for new researchers to enter into the NASA
R&A program. Interdisciplinary thematic studies also have proven effective for
broadening our understanding of the planets. Just as post-mission data analysis
programs capitalize on expertise and excitement associated with a mission, finite
(e.g., three-year) thematic programs build on timely scientific issues related to
planetary research. In view of the importance of this facet of NASA's R&A
program, COMPLEX expresses concern for the delays in implementation of such
programs in recent years.
In the 1990 Update to the Strategy for Exploration of the Inner Planets,
COMPLEX recommended "that NASA should support a vigorous program of data
analysis, basic research, and scientific instrument development." Basic R&A
provides essential continuity and backbone for achieving NASA's goals. As
emphasized in the 1990 report, significant advances have come not only from
new mission data, but also from new ideas and unexpected discoveries made
possible by a vigorous program of basic R&A. Examples include the discovery of
meteorites from the Moon and Mars in Antarctica; geochemical cosmic signatures
on Earth at times of dramatic biologic and climatic change; advanced
computational models allowing tests and constraints for the origin of the Moon by
a catastrophic collision on the Earth; the first imaging of an asteroid by Earth-
based radar; and new insights for Pluto that have dramatically challenged our
view of the last planet in our solar system yet to be explored by a spacecraft.
The Committee on Planetary and Lunar Exploration acknowledges the
sincere efforts by NASA to preserve a balanced research program, but it is
deeply concerned by NASA's view of the R&A program as a financial reserve for
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Assessment of Solar System Exploration Programs 1991 (Chapter 9)
fixing fiscal crises in its flight programs. This practice is harmful to the continuity
and long-term stability of the R&A activities. Moreover, it significantly reduces the
number of young scientists in a field with a median age approaching 50.
Research and analysis programs should not be viewed as another source for
mission reserve funds and need to be insulated from mission cost overruns.
GROUND-BASED AND EARTH-ORBITAL ASTRONOMY
The committee notes that currently there are several projects in various
stages of planning that have a favorable impact on the goals outlined in this
report. They are as follows:
SIRTF (Space Infrared Telescope Facility)—a cryogenically cooled
infrared telescope planned for a high Earth orbit. It will be capable of studying
planetary atmospheres, primitive bodies, interplanetary dust, and potential
extrasolar planetary systems. The inclusion of planetary scientists on the
planning team has helped assure that the telescope will be capable of observing
planetary objects. COMPLEX strongly recommends the completion of this
project.
SOFIA (Stratospheric Observatory for Infrared Astronomy)—an aircraft-
based telescope facility proposed to replace the Kuiper Airborne Observatory
(KAO). A significant portion of the KAO time has gone to planetary projects, and
the committee urges NASA to provide similar opportunities with the SOFIA.
OPT (Orbiting Planetary Telescope)—a 1-meter orbiting telescope
proposed as a joint ESA-NASA project. It will be dedicated to planetary projects
at multiple wavelengths. Excellent planetary research has been done with the
International Ultraviolet Explorer in the past and the OPT would continue this
trend.
Second Keck 10-Meter Telescope—primarily for the detection of
extrasolar planetary systems and proposed as a joint NASA-Keck observatory
facility. It will be operated in an interferometric mode with the first Keck 10-meter
telescope. This would be a potent instrument for search for extrasolar planets.
COMPLEX recommends the development of these and other
interdisciplinary projects. The inclusion of planetary scientists in the planning of
telescope facilities helps in the establishment of critical planetary observational
capabilities. NASA should be commended for including planetary scientists with
relevant expertise on astronomy projects in the past, and the committee strongly
supports the continuation of this practice.
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