Momentum Management of a Spacecraft Equipped with a Dual-Gimbaled Electric Thruster and Rotating Solar Arrays

Abstract Unmodeled forces and torques can cause significant variations in the desired position and attitude of a spacecraft in orbit. This paper focuses on the solar radiation pressure in deep space, which manifests itself in the form of a non-zero net torque on the spacecraft. To avoid unstable growth of the reaction wheel momentum, this paper investigates the use of a gimbaled solar electric propulsion thruster to manage reaction wheel momentum in addition to its primary scope is to provide low thrust to follow a heliocentric trajectory. The thruster is mounted on a dual-gimbaled platform attached to the spacecraft hub. The two degrees of freedom associated with the direction of the thruster are exploited to counteract the momentum build-up on the wheels and reduce the necessity of performing impulsive momentum management. The novelty of this work is the complete kinematic analysis of this system for general spacecraft configurations with such a gimbaled thruster. Large rotating solar arrays provide the required power for the electric thruster and are also used to leverage the solar radiation pressure torque to offload momentum. Emphasis is placed on the problem of determining how to align the thruster in the presence of uncertainties in the center of mass location. The steady-state integral feedback term of the attitude control law is used to inform a sequential least-squares estimator about the location of the center of mass, which is iteratively estimated. The results illustrate that even with small degree-level thruster platform orientation changes, the three-dimensional center-of-mass location can be estimated.