Nonlinear Earth orbit control using low-thrust propulsion

This research is focused on the definition, analysis, and numerical testing of an effective nonlinear orbit control technique tailored to compensating orbit perturbations, as well as possible errors at orbit injection of low- and medium-altitude Earth-orbit satellites. A general, systematic approach to real-time orbit control is presented, under the assumption that the satellite of interest is equipped with a steerable and throttleable low-thrust propulsion system. Two different operational orbits are considered: (a) very-low-altitude Earth orbit and (b) medium-altitude Earth orbit. A feedback control law based on Lyapunov stability theory is proposed and tested. Some remarkable stability properties are established analytically. Then, the overall performance of the nonlinear control at hand is investigated for cases (a) and (b), over 5 years. The effect of satellite eclipsing on available electrical power is considered as well. For mission scenario (a), suitable tolerances on the desired (nominal) conditions allow substantial savings in terms of propellant requirements.