Horseshoe Orbits for Propulsion-Free Exploration of the Martian Moons

摘要

A novel approach to exploring the Martian moons Phobos and Deimos using a stable three-body horseshoe orbit that librates around the L_3, L_4 and L_5 Lagrange points is proposed. This paper presents a theoretical basis for the existence and long-term stability of horseshoe orbits around Mars, and confirms this by simulation. It is found that varying initial semi-major axis is the primary factor affecting the behavior of the horseshoe orbit including the time between encounters with the target moon and the distance to the target moon at closest approach. A horseshoe orbit is demonstrated to result in periodic low-velocity close encounters between a spacecraft and the target moon, with long periods between encounters to transmit data to Earth, and with no requirement for propulsion to maintain the stability of the orbit. This approach is proposed in the context of a conceptual CubeSat-based mission to take advantage of a hypothetical opportunity for a secondary payload on the upcoming JAXA Martian Moon exploration (MMX) mission to the Martian moons.