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

TLDR

Such analyses are essential for missions to small bodies, where mass, gravity, and rotation are unknown until rendezvous and must be incorporated into a redesigned mission profile. The study presents rapid, systematic methods to evaluate the dynamical environment near an asteroid, focusing on the effects of its gravity field and rotation on spacecraft orbits. These methods compute orbit stability and practical proximity limits around the asteroid, using preliminary shape and mass models to assess perturbations. Applying the approach to 433 Eros, the NEAR target, the authors present numerical evaluations based on models derived from the December 1998 flyby.

Abstract

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 Ž eld 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 Ž eld, 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 proŽ le 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, speciŽ cally the computation of orbit stability close to the body and the practical limits on how close the spacecraft can  y to the body before large perturbations are experienced. Numerical computationsof such an evaluationapplied 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  yby of Eros are presented.