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E. Morrow (SIO, UCSD), D.J. Scheeres (UMich), C. R. McInnes (Univ. of Glasgow), D. Lubin (SIO, UCSD)
The inherent capabilities of solar sails and the fact that they need no onboard supplies of fuel for propulsion make them well suited for use in long-term, multiple-objective missions. They are especially well suited for the exploration of asteroids, where one spacecraft can rendezvous with a number of asteroids in succession. The orbital mechanics of solar sail operations in close proximity to an asteroid have been studied recently (Morrow et al., AIAA Paper 2000-4420). It has been found that both hovering and orbiting trajectories are feasible for sustained solar sail spacecraft operations in close proximity to an asteroid. The hovering points allow the sail to fix its location in the asteroid-sun frame at phase angles greater than 90\circ, and can be stabilized using feedback control to sail attitude alone. The orbiting trajectories are naturally stable sun-synchronous orbits, lie near the asteroid-sun terminator plane, and offer good coverage of the asteroid surface, although restrictions on sail acceleration are needed for smaller, Near Earth asteroids.
Our model assumes a spherical, point mass asteroid, a perfectly reflecting solar sail, and a circular asteroid orbit about the sun. All these assumptions can be relaxed without significantly changing the overall conclusions of the current study. For the purposes of this study, we focus only on the behavior of the solar sail spacecraft after rendezvous has been achieved. Limits on the solar sail acceleration and orbital operations are developed as a function of an asteroid's physical and orbital parameters. These relations can be used to design a solar sail capable of sustained close proximity operations about asteroids with a range of physical and orbital properties. The implications of these results for the scientific exploration of asteroids using solar sails are discussed.
Research at the University of California, San Diego, was supported by the National Science Foundation NSF-OPP 98 06941. Research at The University of Michigan was supported by the TMOD Technology Program by a grant from the Jet Propulsion Laboratory, California Institute of Technology which is under contract with the National Aeronautics and Space Administration, and by the NASA OSS Planetary Geology and Geophysics program.
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