Italian star tracker: In-orbit experiences

IST (Italian Star Tracker), embarked as a technological payload on the Argentinean Satellite SAC-C, is a system that autonomously determines its own boresight attitude from stars only. It is composed of an Optical Head (OH) developed by Alenia Difesa Officine Galileo based on a CCD, an Electronic Unit (EU) developed by LABEN with an ERC32 processor and an Application Software developed by Alenia Spazio and Eicas Automazione able to determine the attitude in real time. It is the flight demonstrator of ANDROMEDA, the multi-head autonomous determination system developed by Alenia Spazio together with Eicas Automazione. The paper describes the first quality performances of IST, after two-year continuous operation. IST has been adopted as bus star tracker, after commissioning, in place of the nominal SAC-C bus star tracker which is unable to provide continuously and reliably the required information.