– the intergovernmental organization through which Member States act together
     on matters related to measurement science and measurement standards.
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Circular T
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TT(BIPM) is a realization of Terrestrial Time as defined by the International Astronomical Union (IAU). It is computed annually by the BIPM, based on a weighted average of the evaluations of the frequency of TAI by the primary and secondary frequency standards. It is mostly used in scientific applications requiring long-term frequency stability and high frequency accuracy.

Until the next realization, users can extend TT(BIPM15) after MJD 57379 as:

    TT(BIPM15) = TAI + 32.184 s + 27702.0 ns

Other international metrology data centres:

International metrology publications
SI Brochure
Guides in metrology
Circular T
IERS Conventions Center
Recommended values of standard frequencies
Related articles
International reference timescales
Recent publications of the BIPM Time Department