Frequency comparisons via GPS carrier-phase: jump processing, temperature compensation and zero/short-baseline noise-floors

GPS carrier-phase receivers have been used to produce high quality time/frequency comparisons between clocks and frequency standards. Current ways of processing the carrier-phase data, however, result in phase jumps and data gaps that make the data difficult to use effectively and repeatedly for long datasets. In addition, temperature fluctuations generally perturb receiver output detrimentally. We describe the steps of a simple but effective automated algorithm for comparing frequencies that can compensate for data gaps, day boundary jumps, and other phase jumps as well as for temperature disturbances. We describe process features and focus on zero-baseline noise-floors, measuring Allan deviations of the Deep Space Atomic Clock mission’s receiver down to 1x10-17 at 5x105 seconds, with an upper confidence level of 3x10-17. The zero-baseline noise floors we present give confidence in our algorithm and temperature compensation’s robustness.