Search and analysis on quasi-satellite orbits around Martian moon Phobos

Abstract

Martian moons are of great significances for the planetary science research and thus have been hot targets of deep space explorations for several decades. It is pivotal to find stable orbits around the moons to meet requirements of the scientific exploration. A new orbital dynamics model around Martian moons has been established in this paper within the framework of the Restricted Three-Body Problem consisted of Mars, the moon, and the spacecraft. The non-spherical gravity field of the Martian moon, which is modelled as that of a homogeneous polyhedron, and the eccentricity of the moon’s orbit have been both taken into account. That is to say, the orbital model established is a combination of the Restricted Three-Body Problem and the orbital problem in a non-spherical gravity field of a small body. By using numerical simulations, stable Quasi-Satellite Orbits (QSOs) which start from the equatorial principal axes of Phobos have been searched, and the stability characteristics of the QSOs have been analyzed. The sensitivity of stable orbits with respect to the initial velocity error, the feasibility of global coverage, and the minimum/maximum orbital heights have been analyzed for the stable QSOs. The considerations for selecting QSOs for exploration missions have also been studied. Finally, some typical 2D QSOs and 3D QSOs are selected for further analyses, including their geometric characteristics and potential applications. Through the analyses of several QSOs, we have found that when choosing a stable QSO for a specific mission, comprehensive considerations are needed. The model established in this paper is widely applicable in the orbital dynamics research and orbital design around Martian moons, and it has revealed the basic distribution and characteristics of the stable QSOs around Martian moons, which are crucial for the orbit design of the prober.