Design concept for autonomous operation of KITSAT-3, an experimental LEO microsatellite

KITSAT-3 is a 3-axis stabilized technology demonstration satellite weighing 100 kg and was launched into the 720 km altitude sun synchronous circular orbit by Indian PSLV rocket in May, 1999. As we have only one command groundstation, the contact time is limited and hence, satellite operation was required to be highly autonomous. KITSAT-3 is heavily dependent on centralized on-board computer (OBC) for its autonomous in-orbit operation. Autonomous operation of KTTSAT-3 is implemented in the normal mode housekeeping and the safe mode operation. Battery charge control, operation mode based attitude control, scenario based payload operation and flexible on-board software management are the techniques used for the normal mode operation. For the safe mode operation, two levels of power safe mode control, OBC back-up mode and attitude safe mode control are used. Initial in-orbit operation was successful and the autonomous operation has been achieved by the implemented design concepts.