An interruptionless timekeeping system for space applications using low cost, commercial off-the-shelf (COTS) atomic clocks

We present a new approach to timekeeping on board spacecraft which relies on a relatively large (≅10) number of miniature commercial off-the-shelf (COTS) rubidium atomic clocks, of which a small number (≅4) operate simultaneously to provide ensembled timekeeping. The performance of the “ensembled clock” is expected to be competitive with that of available space clocks; the total number of clocks on the payload provides the required overall mission reliability, and the presence of multiple ensembled operating clocks allows timekeeping and frequency control on board the spacecraft to proceed without interruption, even if one of the operating clocks fails. The clocks are mounted within a pressurized, thermally stabilized container to enable operation in vacuum and to compensate for their relatively high thermal sensitivities