Kinematic registration and shape analysis for locating center of mass in large passive spacecraft

The location of the center of mass of failed or abandoned satellites is a fundamental information for a safe capturing with servicing or removing purposes. The complete observation of the satellite dynamics relative to a chaser spacecraft is often pursued by feeding Kalman filters with positions of a fixed set of features of the target. The difficulties in tracking with continuity this set pose serious doubts on the reliability of such methods. On the other hand, the high uncertainty expected in the position of tracked points makes unfeasible any approach that does not rely on state observers. Actually, this paper presents an estimation of the target center of mass, which is disengaged from attitude dynamics estimation and based only on pure kinematic considerations. As an unconstrained body in space rotates around its center of mass, the study of the finite rotations of the body has to reveal the actual location of this particular point. For allowing a better representation of the body pose evolution, a statistical shape analysis of the detected sets of features was considered. First experimental tests revealed the feasibility of the proposed approach, which does not require the satisfaction of common assumptions like the absence of interruptions in the input data flow.