ESA's PROBA satellite features a high degree of autonomy, both technologically and scientifically. It is build around a powerful command, data and AOCS controller and with its less than 100 kg it is a true microsatellite. The scientific mission of PROBA includes a scanning telescope, which calls for high pointing accuracy and agility. The Advanced Stellar Compass (ASC) provides the pointing knowledge with arc-second accuracy. A description of the PROBA ASC is given and various aspects of the ASC are treated: Handling of solar and lunar blinding and dark and lit Earth horizons in the field of view. The accuracy of the PROBA ASC is analyzed comparing the measurements from the ASC's two camera-heads. Investigation of this Inter-Boresight Angle demonstrates the spacecraft thermal flexures, and models this to arc-second level. The astronomical aberration corrector of the ASC is investigated and confirmed. Finally timing and radiation handling of the ASC is treated.
Acta Astronautica, 2005, Vol 56, Issue 1-2, p. 153-159