Earth-phobos transfer with ballistic trajectory in the sun-mars system

In this paper, the low-cost Earth-Phobos transfer is designed by using the ballistic trajectory in the Sun-Mars system. The spacecraft is firstly captured at a low altitude into a high eccentricity ballistic trajectory, which naturally changes its orbit elements under the solar perturbation. When the ballistic trajectory has the same periapsis distance and inclination as Phobos orbit, the spacecraft will be captured into the target orbit. The property and design procedure of the proposed transfer is discussed. A two-direction shooting scheme and apoapsis Poincaré map are used to find the low-cost transfer opportunity. The two-steps differential correction strategy is applied to match the apoapsis states and a small correct maneuver is added to increase the flexibility of the ballistic transfer. Finally, the integrated trajectory design including interplanetary transfer, ballistic transfer and Phobos insertion is represented. By utilizing Sun’s gravity, the ballistic transfer requires less velocity increment than traditional transfer. It also provides multiple transfer opportunities and flexible periapsis conditions, which can provide a reference for the future Phobos exploration missions.