93-145
Trajectory Design For A Lunar Mapping And Near-Earth-Asteroid Flyby Mission
David W. Dunham* and Robert W. Farquhar*
Abstract
In August, 1994, the unusual asteroid (1620) Geographos will pass very Earth. This provides one of the best opportunities for a low-
cost asteroid flyby mission that can be achieved with the help of a gravity assist from the Moon during the years 1994 and 1995. A Geographos flyby mission, irlcluding a lunar orbiting phase, was recommended to the Strategic Defense Initiative (SDI) Office when they were searching for ideas for a deep-space mission to test small imaging systerns and other lightweight technologies. The goals for this mission, called Clementine, were detined to consist of a comprehensive lunar rnapping phase before leaving the Earth-Moon system to encounter Geographos. This paper describes how the authors calculated a trajectory that met the mission goals within a reasonable total av budget. The paper also describes some refinements of the initially computed trajectory and alternative trajectories that were investigated.
The paper concludes with a list of trajectories to fly by other near-Earth asteroids during the two years following the Geographos opportunity. Some of these could be used if the Geographos schedule can not be met. If the 140 phase angle of the Geographos encounter turns out to be too risky, a flyby of (2102) Tantalus in January, 1995, has a much more favorable approach illumination. Tantalus apparently can be reached from the same lunar orbit needed to get to Geographos. However, both the flyby speed arld distarlce from the Earth are much larger for Tantalus than for Geographos.
*Senior Staff Engineer. The Johns Hopkins University, Applied Physics Laboratory, Johns Hopkins Road, Laurel, Maryland 20723