Design of Attitude Control System of an Axisymmetric Satellite with Gravity Gradient Stabilization and Slow Spinning about Yaw Axis

Attitude control system of satellite with Gravity Gradient stabilization requires high moments of inertia ratio for providing stability and continuous orientation toward Earth. Although, this high ratio causes satellite has small body and reduce mission capability. In this paper, moments of inertia ratio is reduced using a closed form formula based on our previous work, in such a way that it could be provided more missions by augmented solar panels to satellite. Solar orientation could be yielded by rotating satellite about gravity gradient boom (yaw rotation). Interaction between yaw rotation and satellite rotation around Earth causes biased-attitude error in roll axis. To overcome this problem, it is necessary to reduce yaw rotation by adding a reaction wheel toward boom direction. To realization this method, stability criteria of gravity gradient is developed and control law for small and large angles rotation is designed in such a way that angular momentum and moment constraints of reaction wheel to be satisfied. Finally, fine performance of attitude control system will be illustrated with simulation based on specification of an on-orbit satellite and actual consideration