Spacecraft orbital stability zones around asteroid 99942 Apophis

Abstract

In this work, we study spacecraft orbital motion around potentially “dangerous” near-Earth asteroid (99942) Apophis under the combined effects of perturbations from the third-body gravity, asteroid's non-spherical gravitational field, and the direct solar radiation pressure, incorporating possible asteroid's shadow crossings. To identify possibly stable orbital zones around Apophis, we vary initial conditions of the semimajor axis, inclination, and the longitude of ascending node. The stability is defined in terms of spacecraft lifetime in orbits without collisions or escapes. We have found two regions of stable orbits (initially circular) with a lifetime of up to 3 years: the one with small initial radii (about 400 m), lying close to the modified Laplace plane, the other with initial radii of 1.5–2.5 km, lying near the terminator plane. We also compared the cases accounting for full factors to those without shadows to see the influence of eclipse on the stable orbits. Results demonstrate the importance of considering the asteroid's shadow effect in the long-term orbital evolution - the eclipse may significantly change spacecraft lifetime (in years) at low orbits.