Orbital perturbation due to orbit-attitude coupling near asteroids

Purpose – The purpose of this paper is to assess the orbital perturbation caused by the gravitational orbit–attitude coupling of spacecraft in the proximity of asteroids. Design/methodology/approach – The gravitational orbit–attitude coupling perturbation (GOACP), which has been neglected before in the close-proximity orbital dynamics about asteroids, is investigated and compared with other orbital perturbations. The GOACP has its origin in the fact that the gravity acting on a non-spherical extended body is actually different from that acting on a point mass located at the body’s center of mass, which is the approximated model in the orbital dynamics. Besides, a case study of a tethered satellite system is given by numerical simulations. Findings – It is found that the ratio of GOACP to the asteroid’s non-spherical gravity is the order of r /a_e, where r is the spacecraft’s characteristic dimension and a_e is the asteroid’s mean radius. It can also be seen that as r increases, GOACP will also increase but the solar radiation pressure (SRP) will decrease due to the decreasing area-to-mass ratio. The GOACP will be more significant than SRP at small orbital radii for a large-sized spacecraft. Based on the results by analyses and simulations, it can be concluded that GOACP needs to be considered in the orbital dynamics for a large-sized spacecraft in the proximity of a small asteroid. Practical implications – This study is of great importance for the future asteroids missions for scientific explorations and near-Earth objects mitigation. Originality/value – The GOACP, which has been neglected before, is revealed and studied.