Redundancy Management of On-board Computer in Nanosatellites
Satellite bus has subsystems like attitude determination and control system (ADCS); electrical power system (EPS); and communication, command and data handling (C&DH) for operations at different phases of the mission. These subsystems’ requirements are processed and controlled by the on-board computer (OBC) subsystem in the satellite. On-board computer (OBC) subsystem plays a vital role in the functioning of the satellite system; a small malfunction in this system might result in the entire mission failure. For such critical subsystem where on-board manual intervention to repair or replace a failed component is difficult, it is very much essential to have a redundant mechanism. Using redundancy concepts to improve the reliability of systems or subsystems is a well-known principle. This paper describes the architecture of OBC and the redundancy configuration in the nanosatellite. Further, the redundancy management between master and redundant subsystem is explained. This is achieved by first detecting the failure by using an external watchdog timer that monitors master OBC unit along with the redundant. The isolation of the fault signals from the failed unit is controlled by the power control switch.