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This paper studies an observer-based adaptive learning control for spacecraft attitude stabilization subject to actuator fault, parameter uncertainty and external disturbance. Specifically, a new Barrier Function-based Iterative Learning Observer is proposed to estimate the lumped disturbance. Unlike existing iterative learning observer scheme, the newly proposed observer allows the gain matrix to fluctuate in accordance with exact values of the estimation errors, which leads to the estimation errors converges to a predefined neighborhood of zero independent of the adaptive gain matrix in finite time. Then, a composite control law is developed for spacecraft attitude stabilization by combining the newly proposed observer with a robust feedback controller. The stability of the overall closed-loop control system is proved in the Lyapunov framework. Finally, the robustness and effectiveness of the proposed strategy is demonstrated by numerical simulation. [ABSTRACT FROM AUTHOR]

This paper investigates the orbit determination problem for fuel station (FS) in multiple Sun-Synchronous Orbit (SSO) spacecrafts refueling mission. A novel K-M-N transportation network to solve this general refueling problem is proposed, which contains several FSs with their reusable servicing spacecraft (SSC) and a large number of targets. The proposed network allows the FS drifting in a cooperative rendezvous to reduce the fuel consumption considering the J 2 perturbation. Furthermore, one-to-one mode is chosen as the refueling strategy between the FS and the target, which makes it feasible to determine the number and orbit of the FS. In order to achieve such an economical refueling strategy, the problem is formulated as a facility location–allocation (FLA) model, subject to the different demands among targets and the limitation of SSC's capacity. Then, a hybrid Density-Based Spatial clustering algorithm (HDBSCAN) is designed to solve the multi-objective optimization model. Finally, two numerical examples are presented to illustrate the effectiveness and validity of the proposed algorithm. [ABSTRACT FROM AUTHOR]