Spinning-Up Control of a Conical Scanning Imaging Satellite

A conical scanning imaging satellite is designed to acquire wide-swath images by spinning around a certain axis while keeping the axis parallel to the nadir axis. Unlike a spin-stabilized satellite, this type of satellite consistently varies its spin axis in inertial space. Therefore, it is usually triaxial-stabilized. During the spinning process, the pointing of the spin axis is controlled using two orthogonal control torques, while the spin rate is controlled by another control torque. To describe the kinematics of the attitude motion, an error form of $(w,z)$ parameterization is utilized. This parameterization eliminates the need to deal with redundant parameters in Euler–Rodrigues kinematics. In this study, we propose two synchronous spinning-up control strategies considering asymmetric configuration and finite disturbance. These strategies aim to ensure that the spin axis of the satellite points towards the Earth's center and maintains stable tracking. The first strategy is an elementary control with fewer adjustable parameters, suitable for most application scenarios. The second strategy is a fixed-time control with more adjustable parameters, enabling rapid convergence. Both strategies consist of two phases. In the first phase, the satellite undergoes a synchronous spinning-up process, which is faster compared to traditional asynchronous spinning up. In the second phase, the spin angle is stabilized by introducing the retained parameter. Simulation results are presented to demonstrate the effectiveness of the proposed control strategies.