Design of attitude determination and control system for Hokkaido Satellite

This paper describes the design and performance verification of the attitude determination and control system for the Hokkaido Satellite. The main missions of the satellite are earth observation during sunlight and laser communication during sunshade. The purpose of the attitude determination and control system is to stabilize the attitude around three axes within three degrees. The satellite is stabilized by a momentum wheel (MW). The attitude determination system consists of an earth sensor and an inertia reference unit (IRU). Based on the Kalman filter, the determination system can estimate three attitude angles and IRU bias rates without a yaw sensor. The control modes of the satellite are an attitude acquisition mode, a normal mode and a safe-hold mode. For the normal mode of the wheel-stabilized earth pointing satellite, a new pointing control law is proposed. The proposed law simultaneously achieves nutation dumping and angular momentum direction control relative to the orbital coordinate system. The control law consists of pitch angle control by MW, roll and yaw axes control by magnetic torquers (MTQ) and angular momentum control by MTQ. Through numerical simulations, it was confirmed that the determination laws and the control laws can achieve the required attitude accuracy and stabilization time.