Nanosatellite Attitude Stabilization Using Passive Aerodynamics and Active Magnetic Torquing

Abstract

Aerodynamic and magnetic torques have been used to develop a new three-axis attitude stabilization system for a nadir-pointing low-Earth-orbiting spacecraft. The goal is to develop a crude three-axis stabilization system for a 1-kg nanosatellite and to stay within a mass budget of 0.1 kg and an average power budget of 0.06 W. The system uses passive aerodynamic drag torques to stabilize pitch and yaw. The aerodynamic design resembles a badminton shuttlecock and uses thin metallic “feathers” that deploy from the rear of a small cubic main spacecraft bus. The active magnetic control system stabilizes roll and damps pitch and yaw by feeding magnetometer measurements back to magnetic torque coils. It also includes a feedforward term that is based on the expected magnetic field vector direction in spacecraft coordinates when the spacecraft is in its commanded orientation. The system has been tested via simulation. Global stabilization is achieved for all altitudes below 500 km, as evidenced by the system’s ability to capture the nadir-pointing attitude when starting from a tumble. Worst-case pointing errors are below 25 deg per axis at altitudes below 450 km, and these errors can be decreased by a decrease in orbital inclination, asymmetries, or both.