eraTdbtt

[rv, tt1, tt2] = ERFA.tdbtt(tdb1, tdb2, dtr)

Time scale transformation: Barycentric Dynamical Time, TDB, to Terrestrial Time, TT.

Given:

   tdb1,tdb2  double    TDB as a 2-part Julian Date
   dtr        double    TDB-TT in seconds

   tt1,tt2    double    TT as a 2-part Julian Date

              int       status:  0 = OK

tdb1+tdb2 is Julian Date, apportioned in any convenient way between the two arguments, for example where tdb1 is the Julian Day Number and tdb2 is the fraction of a day. The returned tt1,tt2 follow suit.
The argument dtr represents the quasi-periodic component of the GR transformation between TT and TCB. It is dependent upon the adopted solar-system ephemeris, and can be obtained by numerical integration, by interrogating a precomputed time ephemeris or by evaluating a model such as that implemented in the ERFA function eraDtdb. The quantity is dominated by an annual term of 1.7 ms amplitude.
TDB is essentially the same as Teph, the time argument for the JPL solar system ephemerides.

McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), IERS Technical Note No. 32, BKG (2004)

IAU 2006 Resolution 3

This revision: 2021 May 11