Research on hovering control scheme to non-circular orbit

An open-loop control system for hovering at any selected position on spacecraft orbit is first presented given that the satellite＇s engine provides continuous finite thrust. Actually, the hovering states are unstable considering perturbations and thrust errors, so a feedback sliding mode variable structure control, which is adaptive and chattering-free, is designed. Under this feedback control scheme, the high-frequency chattering phenomenon is avoided, while the system stays highly robust at the same time. Simulation results show that the feedback control thrusts are continuous and the steady-states error can be confmed to 10-4 m at the presence of uncertain perturbations. Finally, the feasibility of realizing hovering orbits is analyzed taking the ＂Moliya＂ and geosynchronous Earth orbit （GEO） satellites as examples.