ESA Science & Technology - Simulating stars in the cleanroom

The silver-coloured cylindrical unit in the foreground is the optical head of one of two star trackers, mounted on the hexagonal top panel of the CHEOPS spacecraft platform for this specific test. During on-ground testing of the pointing control loop, synthetic star fields were provided to the star trackers by a dedicated optical stimulation set-up (the black structure covering the aperture of the star tracker). Images obtained by the star trackers are compared with star catalogues to measure the orientation of the spacecraft and adjust the pointing of the telescope.