The singular surfaces of pyramid-type single-gimbal control moment gyroscope (SGCMG) configuration are classified and visualized in the angular momentum space. Continuous impassable and passable singular surfaces in the gimbal angle space is obtained by using the Binet-Cauchy theory, and the relationship between the two spaces is subsequently analyzed. Thereafter, a rapid singularity-escape steering law in the gimbal angle space is proposed to drive SGCMGs to escape from an impassable singular surface. Simulation results demonstrate the effectiveness of the proposed steering law.

In this article, the problem of optimal reconfiguration control for large-scale satellite cluster with collision avoidance constraints and uncertainties is considered. Based on receding horizon control and successive convexification methods, a decentralized closed-loop control algorithm is proposed. First, the optimal control problem is converted into a series of convex optimization subproblems by linearization and discretization. These subproblems can be efficiently solved in polynomial time through the successive convexification approach. Second, to alleviate the communication and computational burdens on satellites and enhance scalability, the successive convexification technique is integrated with the receding horizon framework. This approach enables the continuous updating of optimized control commands, resulting in high-precision closed-loop control for satellite cluster reconfiguration. Third, to maintain collision-free satellite operations throughout the mission, an anti-collision strategy is proposed to address potential collisions between adjacent discrete points. Furthermore, the concepts of trajectory freezing and parallel computing are utilized to improve computational efficiency. Finally, numerical simulation results are presented to demonstrate the effectiveness, robustness, reliability, and real-time applicability of the proposed method under constraints and uncertainties.

Rotating mirror-based space cameras are susceptible to mirror misalignment due to the severe vibrations experienced during rocket launch and the harsh, variable conditions of the space environment, which can result in deviations of the camera’s line of sight. To mitigate this risk, this study proposes a simulation-based on-orbit calibration method for quantifying rotating mirror misalignment using a system of pointing vector equations. The method employs star coordinates as a reference to establish the reference pointing vector for stars, while simultaneously developing a model of the rotating mirror imaging system. By incorporating a misalignment matrix, the actual pointing vector of star points is derived. Subsequently, the reference star pointing vector and the actual star point pointing vector are combined to formulate a system of pointing vector equations. Solving these equations enables precise measurement of the rotating mirror’s rotational misalignment without requiring additional spaceborne equipment. Through simulations, the three-axis misalignment of the rotating mirror is deduced from imaging pixel coordinates, given the known right ascension and declination of reference star points. The influence and patterns of three-axis misalignment on pointing accuracy are analyzed separately. Although validation based on real measurement data remains to be carried out in future work, this simulation-based method provides a theoretical foundation for the calibration of internal orientation elements of space cameras equipped with moving components.