Capture and Visual Tracking Control of Early Warning Spacecraft Based on a Two-Axis Turntable

In this work, we deal with the pointing control problem for the whole tracking process of a non-cooperative object via a two-axis turntable-based early warning satellite, where the initial target acquisition process and the subsequent visual tracking process are addressed respectively. First, to conquer the capture error caused by the camera assemble error and the inconsistency of the center of the viewing field for multiple channels of the camera, a high-accuracy capture protocol with bias compensation is devised by utilizing the image kinematics of the turntable and the satellite. Second, an image-based nonlinear visual servoing controller via a novel velocity estimator is developed, where the angular rate of the turntable and the satellite is involved to predict the image velocity. In addition, the planning scenario for the expected image trajectory is introduced to improve the performance of the transient period. Finally, on-board experiment is performed to testify the effectiveness of our methodology.