Visual Motion Estimation for Tumbling Satellite Capture

Robotic service vehicles are presently seen as a viable means for performing satellite maintenance and ESA (European Space Agency) is presently investigating the possible characteristics and potential of a Geostationary Service Vehicle (GSV). A stereovision tracking system should be included in this GSV to help the operator track and capture the target satellite. This paper deals with a system, called TV-Trackmeter, previously developed for underwater robotics, featuring contemporary tracking and 3D measurements of more points. It is capable of providing rigid body real time pose evaluation and it is fitted with algorithms to recover the lost tracked targets. Trials have been carried out in the ESA-ESTEC premises, in order to evaluate the applicability of this concept to the satellite capture. A satellite mock-up has been moved by an industrial manipulator to simulate real motion of a free object in space. The results have proved the soundness of the approach, featuring for the linear position accuracy in the order of ±3 [mm] @ 3.5 [m] for the x and z axes and ±5 [mm] @ 3.5 [m] for the y axis. As regards the angular position error about the y axis is the smaller one, about ±0.5 [deg], while it is ±1 [deg] on the remaining axes.