Nonlinear orbit control for earth satellites using low-thrust propulsion

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