Synchronization Scheme Among Satellite Systems for Space Applications

Abstract

In present satellite systems both main and redundant control systems work independently with reference to its own generated clocks. Both systems perform its functions independently and process the data, but only the selected system carry out command execution, actuator drive and payload operations. In future space missions, if both main and redundant systems need to execute and validate to carry out different critical operations seamlessly, there is a requirement to synchronise them. This paper proposes the synchronisation scheme which is going to be introduced in Indian satellite systems for the first time. This scheme is realised through FPGA based logics, cycle flag exchange through hardware interface, sync loss detection, relative clock drift estimation through software logics and on-board drift correction. Both main and redundant satellite systems are configured as master and slave which are synchronised within a defined window period. Provision exists to disable sync in case of sync loss and enables auto-drift correction to sustain the drift between systems. This scheme can be extended to all the satellite systems for synchronisation between different navigation and guidance control (NGC) systems and also for drift estimation and auto correction.