Space Studies Board

Scientific Assessment of the Strategic Defense Initiative Organization's Integrated Sensor Experiment (CLEMENTINE)

The Space Studies Board's Committee on Planetary and Lunar Exploration (COMPLEX) conducted a review of the Strategic Defense Initiative Organization's (SDIO) Integrated Sensor Experiment (hereafter referred to as the Clementine mission) at its April 27-28, 1992, meeting in Washington, D.C. The committee's intent was to determine the extent to which the possible collateral scientific return from this technology demonstration mission might address past COMPLEX recommendations for scientific exploration of the Moon and asteroids. 1,2,3

During its meeting, the committee was briefed by Drs. Peter Rustan (SDIO Clementine project manager), Carl Pilcher (NASA scientific liaison to the Clementine mission), and Carle Pieters and Eugene Shoemaker (members of the mission's Science Working Group). Based on these presentations, COMPLEX concludes that Clementine's observations of the Moon and of the asteroid 1620 Geographos provide a significant opportunity to advance our scientific understanding of these objects. Although the planned observations cannot completely satisfy the highest scientific objective—determining the geochemistry of the Moon 4,5—due to lack of imaging spectroscopy and gamma-ray spectroscopy, they will provide a global map of lunar lithology and will substantially improve our geodetic and topographic knowledge of the Moon. Likewise, Clementine's asteroid observations will contribute to COMPLEX's foremost asteroid science objective, which is to "determine their diversity of composition and structure." 6 This contribution will, however, be incomplete because of the rapidity of the flyby, Clementine's limited instrument complement, and its inability to measure the asteroid's mass. 7

The filters provisionally selected for Clementine's imaging systems will be capable of distinguishing different surface units and will measure well the range of variability of surface rock types. Close-up observations of another asteroid (in addition to Galileo's observations of 951 Gaspra in November 1991, and planned observations of 243 Ida in August 1993) are, in themselves, scientifically valuable.

COMPLEX concludes that new discoveries are possible from this mission and that technical demonstration of SDIO's innovative lightweight sensors on a small mission may provide valuable experience and new options for future planetary missions developed by NASA. The Clementine mission is, therefore, supportive of previous COMPLEX statements 8,9 concerning NASA's development of a small-mission program for planetary exploration.

The committee was concerned, however, by the apparent absence from Clementine program planning, as presented at the April meeting, of formalized procedures for: 10

ensuring the scientific calibration and documentation of the selected instruments,
validating and archiving scientific data,
performing scientific studies using the acquired data, and
conducting appropriate ground-based correlative studies.

COMPLEX recommends that SDIO and NASA act together to strengthen these scientifically vital aspects of the program.

1. 1990 Update to Strategy for Exploration of the Inner Planets, Committee on Planetary and Lunar Exploration, Space Studies Board, National Academy Press, Washington, D.C., 1990.

2. Strategy for Exploration of the Inner Planets: 1977-1987, Committee on Planetary and Lunar Exploration, Space Studies Board, National Academy Press, Washington, D.C., 1978.

3. Strategy for the Exploration of Primitive Solar-System Bodies—Asteroids, Comets, and Meteoroids: 1980-1990, Committee on Planetary and Lunar Exploration, Space Studies Board, National Academy Press, Washington, D.C., 1980.

4. Assessment of Solar System Exploration Programs: 1991, Committee on Planetary and Lunar Exploration, Space Studies Board, National Academy Press, Washington, D.C., 1991, page 3.

10. Data Management and Computation, Volume 1: Issues and Recommendations, Committee on Data Management and Computation, Space Science Board, National Academy Press, Washington, D.C., 1982.