Evaluation of the Dynamic Environment of an Asteroid: Applications to 433 Eros

Methods of analysis to quickly and systematically evaluate the dynamical environment close to an asteroid are presented, concentrating on the effect of the asteroid's gravity field and rotation state on a spacecraft orbit. Such an analysis is useful and needed for missions to small solar system bodies such as asteroids and comets, where the true mass, gravity field, and rotation state will not be 'known until after the spacecraft rendezvous with the body and these quantities are estimated. Generally, after these quantities have been estimated, the complete mission profile must be redesigned in accordance with the actual values found at the asteroid. An integral part of this redesign is the characterization of dynamics close to the asteroid, specifically the computation of orbit stability close to the body and the practical limits on how close the spacecraft can fly to the body before large perturbations are experienced. Numerical computations of such an evaluation applied to the asteroid 433 Eros, the target of the Near Earth Asteroid Rendezvous (NEAR) mission, using preliminary models of the asteroid obtained during NEAR's December 1998 flyby of Eros are presented.