All-Electric Spacecraft Precision Pointing using Model Predictive Control

Recent technological advances in the development of electric microthrusters pave the way to the successful diffusion of all-electric spacecraft. Since pointing accuracy is a key requirement for space platforms, suitable control systems accounting for the peculiarity of electric on/off actuators have to be devised. In this paper, an attitude control system (ACS) for spacecraft equipped with cold gas and electrothermal xenon microthrusters is presented. The number of thruster firings, which has a key impact on the thruster lifetime, is explicitly taken into account in the control design phase. By adopting a model predictive control (MPC) approach, a cost functional including both fuel consumption and number of firing cycles is minimized at each time step, within a receding horizon scheme. The effectiveness of the proposed ACS is validated on a sample GEO mission and its performance is compared with different control laws involving on/off actuators.