Abstract: To solve the problem of the unexpected disturbance to the Halo orbit of the Chang’e-4 relay satellite caused by the frequent momentum wheel unloading under the control of thrust, the influence of the momentum wheel unloading on the mission-orbit configuration and momentum cumulative rules are analyzed qualitatively, and the mathematic relationship between the amount of momentum change and velocity increment is given. Based on the prediction of the momentum unloading time and variation, a combined control method of the mission orbit-keeping maneuver and momentum wheel unloading is put forward. Through optimizing the configuration-keeping objective offset of the Halo orbit, a goal of eliminating the adverse effects of the momentum wheel unloading on the orbit configuration is achieved, with a longer orbit-keeping period and less fuel consumption, and besides a solution method of the control objective offset is given. The experimental results on the measured profiles verify the validity and feasibility of the proposed method.

Key words: Chang’e-4 relay satellite, Halo orbit, Momentum wheel unloading, Orbit maneuver, Combined control, Offset optimization, Sunlight pressure