1 SMALL BODY LANDING ACCURACY USING IN-SITU NAVIGATION

Spacecraft landings on small bodies (asteroids and comets) can require target accuracies too stringent to be met using ground-based navigation alone, especially if specific landing site requirements must be met for safe-ty or to meet science goals. In-situ optical observations coupled with on-board navigation processing can meet the tighter accuracy requirements to enable such missions. Recent developments in deep space navigation ca-pability include a self-contained autonomous navigation system (used in flight on three missions) and a landmark tracking system (used experimen-tally on the Japanese Hayabusa mission). The merging of these two tech-nologies forms a methodology to perform autonomous onboard navigation around small bodies. This paper presents an overview of these systems, as well as the results from Monte Carlo studies to quantify the achievable landing accuracies by using these methods. Sensitivity of the results to var-iations in spacecraft maneuver execution error, attitude control accuracy and unmodeled forces are examined. Cases for two bodies, a small asteroid and on a mid-size comet, are presented