NIST-USNO time comparisons using two-way satellite time transfers

Time comparison data between UTC US Naval Observatory (USNO) and UTC US National Institute of Standards and Technology (NIST) is presented along with some analysis of that data. Second-to-second raw difference data is white and with no discernible slope for a 300-s measurement; a simple mean is computed for the value of the time comparison. Long-term sigma /sub y/( tau ) results are consistent with expected results of a comparison between NIST and USNO, and in-cabinet loop tests of the two-way satellite equipment point to system noise being a factor of 10 below the stability of these results. Therefore the noise contribution due to the two-way time transfer method is assumed to be negligible. The results show that the measurement time could be reduced from 300 s to 100 s with little or no compromise in precision even with a C/N/sub 0/ as low as 55 dB-Hz.<
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