Attitude Optimization Control Method of Agile Optical Small Satellite for Nonparallel Ground Track Imaging

Nonparallel ground track imaging of optical remote sensing satellite is an efficient imaging mode which could realize one-time transit imaging of complex observation tasks due to its fast and flexible imaging capability, and has attracted more attentions in the earth observation field recently. In this paper, an off-line attitude trajectory planning and on-line moving horizon attitude tracking control scheme based on optimal control idea is designed to satisfy the imaging requirement of high-performance attitude control oriented to nonparallel ground track imaging. Considering the entire satellite attitude adjustment of the drift angle, based on the geometric relationship of sapce vectors and the coordinate transformation principle, the three-axis attitude calculation of the precise pointing of key feature targets in the interested ground curve strip is conducted. Taking the attitude orientation as the constraint, the pseudospectral method is used following the established agile satellite control model to design the optimal trajectory of the attitude manever and the feedforward control torque of actuator for nonparallel ground track imaging. A moving horizon tracking control law based on the nonlinear error control model is designed to realize the high-precision attitude tracking control. The feasibility and effectiveness of the proposed control scheme are illustrated by numerical and imaging simulations.