Fine positioning algorithms for the ESA/PROBA-3 formation flying mission

PROBA-3 is the forth of the PROBA technological mission designed by the European Space Agency. The main purpose of PROBA-3 is to demonstrate the capabilities of two different spacecraft to perform in-orbit formation flight. Furthermore, the two satellites will form a scientific instrument, a solar coronagraph, for acquiring relevant data related to the corona of the Sun. In order to make the mission feasible, several novel technologies compose the mission formation flight system. The Shadow Position Sensor (SPS) system is one of the metrological systems designed for providing the satellite relative position with an high level of accuracy.This paper describes the algorithm developed for providing the spacecraft relative position to the mission Guidance and Navigation Control System (GNC). Furthermore, the achieved results in terms of precision are presented. Lastly, an overview of the implemented logic, from the measurements acquisition to the computed position, is provided.