Guidance schemes for low-thrust LEO-GEO transfers

A new, simple, robust method for onboard spacecraft guidance for a LEO-GEO transfer of a solar electric propulsion (SEP) spacecraft is presented. The guidance problem is formulated by using a trajectory tracking approach. The tracking guidance method uses orbital averaging to approximate the dynamics of the spacecraft and blends optimal feedback control laws for pitch and yaw steering. The performance of the tracking guidance scheme is tested under idealized circumstances as well as under a variety of orbit perturbations. Numerical results and a discussion of the attributes of the method are presented. In addition, a trajectory re-optimization method is presented for significant deviations between the guided and the reference transfer. The method is intended to be simple and computationally efficient for autonomous implementation. Performance of the re-optimization method for a variety of deviations from the reference trajectory is provided.