CMG momentum management for spacecraft in inertial frame

CMG momentum management aims to slow down the accumulation of CMG momentum through active attitude adjustments. This paper discusses the momentum management problem in the inertial space which can be mainly divided into two parts: dynamics and constraints analyses and optimal controller design. In the analysis part, the required stable operating attitudes and the corresponding constraints for successful momentum management are presented. The analyses show that spacecraft with momentum management are required to keep one of their principal axes of inertia perpendicular to the orbital plane. Due to the uncertainty of the inertia property, the requirement of absolute perpendicularity is difficult to realize. To solve this problem, the second part of the paper presents an optimal momentum management controller, where CMG momentum is feedback controlled to avoid momentum accumulation. Theoretical analyses and simulation results show that the CMG momentum oscillates periodically under the impact of gravitational and aerodynamic torque with no significant growth in the magnitude when managed in the inertial space.