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