The in-flight calibration procedures of the Shadow Position Sensors (SPS), a very accurate optical metrology system of the ESA/PROBA-3 formation flying mission

The PROBA-3 is a European Space Agency (ESA) mission devoted to obtain, as never before, highly accurate formation flying. A couple of satellites will works together as an externally occulted solar coronagraph. The distance between the two satellites is of 144 meters and the required longitudinal accuracy of the relative positioning is better than 1 mm. In this proceeding the in-flight calibration of one of the most accurate metrology subsystem, the SPS (Shadow Position Sensors), will be presented.