Propellant-efficient station-keeping using a hybrid sail in the Earth-Moon system

The problem of propellant-efficient station-keeping using a hybrid sail in the Earth-Moon system is investigated in this paper. To achieve high-precision station-keeping and minimize propellant consumption, the problem is addressed from perspectives of reference orbits design and control strategy design. A high-fidelity model of a hybrid sail, which consists of a solar electric propulsion (SEP) system and a solar sail covered by reflectivity control devices (RCDs), is exploited for reference orbits design in the Earth-Moon system using numerical methods. These hybrid-sail perturbed halo and Lyapunov orbits are parameterized by the sail's reflectivity and are inherent unstable. An orbit-attitude control strategy is proposed for station-keeping which is composed of three parts: a nonlinear disturbance observer (NDO)-based optimal periodic orbital controller, SEP acceleration optimization, and a NDO-based robust backstepping attitude controller. In particular, RCDs are used in both orbital control and attitude control. Numerical results show that the proposed control strategy can guarantee high-precision station-keeping and effective reduction in propellant consumption.