An Accurate Local Traceable Time-Scale For Calibrating GPS Time-Transfer Products

About this Article
This article by Robin Giffard and Bob Pitcock was presented at the NCSL International 2000 Symposium and published in the Proceedings.

Abstract

We have recently established a stable time-scale in the Standards Laboratory at the Santa Clara site of Agilent Technologies to provide a real-time reference for developing and testing GPS time-transfer products. The time-scale consists of a high performance caesium frequency standard that is steered to follow UTC(USNO,MC) using the output of a commercial GPS-disciplined oscillator. To provide an independent calibration, and to determine the overall accuracy of the time-scale, we also carry out common-view time-transfer with USNO according to established practice. The time-scale and its calibration system are assembled from standard, off-the-shelf, components. In the paper we discuss the stability of the time-scale, and the accuracy of its calibration. Data obtained over several months has shown that the rms deviation of the time-scale is smaller than 10 nanoseconds. It is estimated that the traceability to UTC(USNO,MC) is better than 25 ns. The factors limiting noise and accuracy are discussed, and possible refinements are suggested.

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An Accurate Local TRaceable Timescale for Calibrating GPS Time-transfer Products