A New Realization of Terrestrial Time

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.

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Document Details

Document Type
Technical Report
Publication Date
Sep 01, 2004
Accession Number
ADA427981

Entities

People

  • G. Petit

Organizations

  • International Bureau of Weights and Measures

Tags

Communities of Interest

  • Materials and Manufacturing Processes

DTIC Thesaurus Topics

  • Accuracy
  • Atomic Clocks
  • Blackbody Radiation
  • Clocks
  • Computations
  • Dead Time
  • Electronic Mail
  • Frequency
  • Frequency Shift
  • Frequency Standards
  • Intervals
  • Measurement
  • Standards
  • Steering
  • Test And Evaluation
  • Time Intervals
  • Uncertainty

Readers

  • Geochemistry
  • Positioning, Navigation, and Timing (PNT) Technology.