Robust Minimum-Fuel Orbit Transfers Taking into Account Thruster Under-Performance

In the life of a spacecraft, the Launch and Early Operational Phase (LEOP) is one of the most critical, because the knowledge of the behavior of the SpaceCraft (S/C) platform is still uncertain. This is in particular true for the propulsive maneuvers performed during the first phases of a mission, when the performance of the spacecraft and thrusters is still unknown. The maneuvers that modify the trajectory can be carefully planned on ground and executed by the spacecraft under operator supervision or can autonomously be computed by the on-board software. In both cases the maneuvers are traditionally computed and optimized considering specific nominal values for the spacecraft performance (nominal case), while the robustness of the designed trajectory is tested against one or more identified worst-case scenarios or Monte-Carlo simulations. The trajectory design improving the robustness of the obtained solution is considered an interesting topic of discussion (Oguri and McMahon, Journal of Guidance, Control, and Dynamics. 45(1):84–102, 2022; Ozaki et al., Journal of Guidance, Control, and Dynamics. 43(4), 2020; Di Carlo et al., Robust optimization of low-thrust interplanetary transfers using evidence theory. 29th AAS/AIAA Space Flight Mechanics Meeting, Vol. 168: pp. 339–358, n.d.; Zavoli et al. Journal of Guidance, Control, and Dynamics. 44(8): 1440–1453, 2021). The problem proposed for discussion is how to find a robust control law that takes into account dramatic thruster underperformance. The insertion of a spacecraft in a highly elliptic orbit with multiple apogee burns is considered as an example and the effect of non-nominal thrust in the first apogee maneuver. The approach is extended to the problem of cooperative deployment of two satellites constellation. An indirect optimization method is proposed in order to find a robust optimal control law that guarantees performance even in such an event (Simeoni, Cooperative deployment of satellite formation into highly elliptic orbit. PhD Thesis, 2013).