Sifting Through Nine Years of NIST Clock Data with TA2

We have extended the new TA2 post-processed time scale at the NIST beyond our previous reports to include all of the period from January 1984 to December 1992. Derived from the ensemble of clocks at the NIST, this time scale includes the benefits of several recent refinements to the algorithm. By iteratively running the algorithm on the ensemble clock data and characterizing anomalous behaviour in the dominant individual clocks of the ensemble between iterations, we obtain an optimized scale which benefits from the informed anticipation of that anomalous behaviour and demonstrates an overall decrease in scale disruption. Herein we discuss changes to the TA2 algorithm that we made while processing the eight-year run, our method of characterizing anomalous behaviour in individual clocks, the way unanticipated anomalous behaviour is dealt with by the algorithm, and our resulting nine-year time scale.

[1]  Peter V. Tryon,et al.  Estimation of Parameters in Models for Cesium Beam Atomic Clocks. , 1983, Journal of research of the National Bureau of Standards.

[2]  T. Weissert,et al.  AT2, a new time scale algorithm : AT1 plus frequency variance , 1991 .

[3]  M. Weis,et al.  TA2, a time scale algorithm for post-processing: AT1 plus frequency variance , 1990 .

[4]  M. A. Weiss,et al.  A study of the NBS time scale algorithm , 1989 .

[5]  Marc A. Weiss,et al.  Confidence of the three-point estimator of frequency drift , 1993 .

[6]  Donald B. Percival.  The U. S. Naval Observatory Clock Time Scales , 1978, IEEE Transactions on Instrumentation and Measurement.

[7]  D. W. Allan,et al.  Stochastic models for atomic clocks , 1983 .

[8]  F. L. Walls,et al.  Characterization of frequency stability in precision frequency sources , 1991, Proc. IEEE.

[9]  D. W. Allan,et al.  Time and Frequency (Time-Domain) Characterization, Estimation, and Prediction of Precision Clocks and Oscillators , 1987, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[10]  Peter V. Tryon,et al.  Continuous time series models for unequally spaced data applied to modeling atomic clocks , 1987 .

[11]  Arthur Gelb,et al.  Applied Optimal Estimation , 1974 .

[12]  David W. Allan,et al.  Recent improvements in the atomic time scales of the National Bureau of Standards , 1983 .

[13]  Chak Ming Chie,et al.  Theory of oscillator instability based upon structure functions , 1976, Proceedings of the IEEE.

[14]  David A. Howe,et al.  Properties of Signal Sources and Measurement Methods , 1981 .

[15]  Peter V Tryon,et al.  Estimating Time From Atomic Clocks. , 1983, Journal of research of the National Bureau of Standards.

[16]  S. R. Stein,et al.  REPORT ON THE TIMESCALE ALGORITHM TEST BED AT USNO , 1989 .

[17]  D. W. Allan,et al.  Statistics of atomic frequency standards , 1966 .

[18]  J. Rutman,et al.  Characterization of Frequency Stability: A Transfer Function Approach and Its Application to Measurements via Filtering of Phase Noise , 1974 .

[19]  J. Rutman.  Characterization of phase and frequency instabilities in precision frequency sources: Fifteen years of progress , 1978, Proceedings of the IEEE.