Landing Site Selection Using a Geometrically Conforming Footprint on Hazardous Small Bodies

Abstract

In recent years there has been a great deal of research and development pertaining to the landing of spacecraft on small bodies, such as asteroids. The capabilities to identify and avoid large rocks and other hazards on the surface of small bodies have seen significant improvement. However, many current techniques search for a location on the surface that contains no hazards within a scaled square, circular, or elliptical footprint. A challenge with this approach on asteroids with highly hazardous terrain is that such acceptable landing locations may be few and far between, or may not even exist at all. This paper proposes the use of a geometrically conforming footprint to significantly widen possible landing regions. An optimization technique that uses such a noncircular/elliptical footprint is formulated for a landing location selection algorithm. Coarse and fine variations for determining a landing location are developed and compared for their landing site selection performance as well as their computational effort. The algorithms to find a landing pose close to some desired landing location are constructed assuming a polygonal model of the lander and the obstacle regions. Numerical simulations illustrate the advantages of the geometrically conforming footprint over a circular one. Further, while the fine search algorithm shows better results in placing the lander close to an obstacle, the coarse search algorithm shows comparatively strong results with significantly less computational effort.