A small platform application for close Inspection of an out of control satellite

The field of space proximity operations such as on-orbit inspection, refueling, repair and debris removal has been recently exploring new innovations for what technology and application scenarios concern. For this scope, small orbiting platforms, despite their limited power and operative capacity, represent a low-cost solution for the majority of proximity missions. Regarding mission architecture, various researches have been carried out to analyze the feasibility of several practical applications in a proximity operation scenario. In this sense, GNC systems, which play a fundamental role for the successfulness of the mission, have undergone relevant improvements. Optical navigation has proved to be a reliable solution for the navigation system, optimal path planning algorithms have been augmented with secure and robust collision avoidance, while control strategies offer satisfying performance in terms of desired position and velocity tracking. The present research shows a possible and feasible application of a small platform (chaser) for the close inspection of an uncontrolled, un-cooperative, Earth-orbiting satellite (target). In an initial phase of the mission, the chaser will follow a closed relative orbit (Parking Orbit) around the target and use measurements acquired from a passive camera and a range sensor in order to estimate target’s relative position, velocity, orientation, angular motion and shape. By means of the acquired information, a set of relevant viewpoints for a close and clear inspection of the target is evaluated. As a second step, starting from the Parking Orbit, the chaser will perform a rendezvous maneuver to reach one of the viewpoints, selected as the optimal among all. The Approach Trajectory followed in this phase is computed to be optimal from a propellant consumption point of view and free of collisions with the target. The desired trajectory will be tracked by implementing an impedance control law. Once the viewpoint has been reached, the chaser will maintain the relative position and orientation while performing the inspection by means of a camera mounted on a robotic arm. At the end of this operation, the chaser will transfer to the subsequent viewpoint, following an optimized and safe path. The mission will be achieved once all the viewpoints have been visited. In the paper rigorous analytical formulations of the relative dynamics, estimate process, optimal path planning and control strategy will be presented. Additionally, the feasibility of the proposed architecture will be evaluated through numerical simulations on some test case scenarios.