A Stellar Reference Unit Design Study for SIRTF: The ASC-HP

A design study for a stellar reference unit, or star tracker, for SIRTF was conducted in FY96 in conjunction with the Tracking Sensors Group of the Avionic Equipment Section of JPL. The resulting design was derived from the Oersted, autonomous, Advanced Stellar Compass, star tracker. The projected performance levels for SIRTF are based on actual, real sky, test data taken at the JPL Table Mountain Observatory and at the University of Hawaii, Mauna Kea Observatories in conjunction with JPL. This performance is projected to have a staring mode NEA of only 0.037 arcseconds (both BOL and EOL) and a precision of 0.502 (BOL) and 0.504 arcseconds (EOL), all RMS. These remarkable results are achieved at low cost with a head mass of less than 2.5 kg and a power dissipation of only 400 mW. The low power and mass, together with an operating temperature of about -40 C greatly ease the difficult problems of star tracker integration with the cryogenic telescope structure.