GPS IIR RUBIDIUM CLOCKS: IN-ORBIT PERFORMANCE ASPECTS

摘要

The GPS Block IIR rubidium clocks have proved to be the best performers in the currentrnGPS constellation, starting with the first IIR operational clock (launched on July 23, 1997).rnThis discussion covers a number of topics, including the frequency accuracy, the frequencyrnvariation, and the projected lifetimes of these clocks. The performance of these clocks in orbitrnand their life expectancy are compared with that experienced with previous GPS clocks. Thernsuperior performance and lifetimes of the GPS IIR Rb clocks are highlighted. Because thesernclocks are so well behaved, it has been possible to detect various features and phenomena thatrnwere not previously detectable. The full drift of the IIR clocks is not observed by the userrnbecause of onboard cancellation by the Time Keeping System. The diagnostic and reprogrammabilityrncapability of the GPS IIR Satellites allows these discrepancies to be addressed.rnThe long-lived features of the clocks indicate that they will outlive the GPS satellite missionrnduration.