Abstract: Terrestrial Time TT is a time coordinate in a geocentric reference system. It is realized through International Atomic Time TAI, which gets its stability from some 200 atomic clocks worldwide and its accuracy from a small number of primary frequency standards (PFSs), whose frequency measurements are used to steer the TAI frequency. Because TAI is computed in real time and has operational constraints, it does not provide an optimal realization of TT. The BIPM, therefore, computes another realization TT (BIPM) in postprocessing, which is based on a weighted average of the evaluations of TAI frequency by the PFSs. The procedures to process PFS data have been recently updated and we consequently propose an updated computation of TT (BIPM). We use all recently available data from new Cs fountain PFS and a revised estimation of the stability of the free-running atomic time scale EAL on which TAI is based. The performance of the new realization of TT is discussed and is used to assess the accuracy of recent PFS measurements.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Conference paper |
| Pages: |
13 |
| Report Date: |
SEP 2004 |
| Report Number: |
A189724 |
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