LARGE CONSTELLATION DE-ORBITING WITH LOW-THRUST PROPULSION

This paper deals with the propulsive phase of de-orbiting phase for coplanar sat-ellites in large constellations. The design is conducted via two layers: the first layer is to design a time-optimal deorbiting trajectory for a single satellite; the second layer is to find the optimal de-orbit timing for each satellite to start the de-orbiting in order to minimize the total transfer time as well as the inner con-stellation collision risk. For the first layer, two de-orbit strategies are consid-ered: the first strategy aims at lowering the perigee; the second strategy aims at reaching a natural de-orbiting corridor. For each strategy, the quasi time-optimal steering law is developed, and the secular variations of the orbital elements are derived by using the averaging technique. For the second layer, the inner con-stellation collision risk is evaluated by miss distance; the optimal de-orbit tim-ings are found for different de-orbit sequences by using a multi-objective opti-mization technique.