Formulation of Torque-Optimal Guidance Trajectories for a CubeSat with Degraded Reaction Wheels

This paper presents the theory and design of a torque-optimal guidance algorithm for CubeSat applications. CubeSats and nano-satellites provide mission-flexible low-cost platforms for the academic and scientific communities to conduct cutting-edge research in the harsh environment of space. The mission life of nano-satellites may be limited by the attitude actuators, and it is therefore beneficial to reduce torque and angular momentum usage during reorientation maneuvers. The algorithm focuses on being computationally lightweight and robust, while including the effects of gyroscopic moments, environmental torques, and degraded reaction wheels. Results indicate that this torque-optimal guidance algorithm demonstrates substantial improvements in performance and pointing accuracy over an Eigenaxis controller for similar maneuvers, with low to moderate computational overhead. In doing so, it presents a significant advancement towards the development of intelligent GN&C systems for small satellites.