Autonomy requirements for the Space Infrared Telescope Facility

The Space Infrared Telescope Facility (SIRTF) will be launched in December 2001 into an Earth-trailing heliocentric orbit, receding from the Earth at a rate of approximately 0.1 AU per year. SIRTF carries three science instruments; taken together, these instruments provide imaging and spectroscopic capability at wavelengths from 3 μm to 180 μm. After an initial 60-day checkout and calibration period, SIRTF will spend the next five years conducting a variety of observing campaigns, including searches for brown dwarfs, superplanets, and planetary disks. SIRTF´s Ground System will schedule occasional one-hour communications sessions with the observatory, usually once or twice per day. In between communications sessions, SIRTF will operate autonomously, working its way through a ground-provided observing list that the ground will update once or twice per week. SIRTF´s total science data return will be highly influenced by its ability to perform time-efficient observations. The helium supply has been sized to last five years, and the primary mission will end when that supply has been expended. The limited frequency and duration of the planned flight-ground communications sessions, combined with the desire to perform time-efficient observations between those communications sessions, has motivated SIRTF to levy particular types of autonomy requirements. This paper describes those autonomy requirements, and some initial plans for implementing those requirements