Analysis of Clock Modeling Techniques for USNO Cesium Mean

Abstract : The U.S. Naval Observatory (USNO) maintains an ensemble of commercial cesium frequency standards. The mean time scale generated from this ensemble is used as the long term frequency reference for all USNO clocks. Maintenance of this mean is currently done in a post-processing fashion with clock models being adjusted as far as 75 days into the past. While this method ensures the resulting mean is stable in the past, it can create errors in the near-real-time determination of the frequency of the mean. This in turn adds to the uncertainty in the determination of the clock frequencies relative to the mean. Multiple methods for adjusting clock models in near real time are examined and tested on actual clock data.