SIFTING THROUGH 9 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.