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# tdbtt

erfa.tdbtt(tdb1, tdb2, dtr)

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

  Parameters:
    tdb1 double array
    tdb2 double array
    dtr double array
  Returns:
    tt1 double array
    tt2 double array

  Notes

  Wraps ERFA function `eraTdbtt`. The ERFA documentation is:

      - - - - - - - - -
       e r a T d b t t
      - - - - - - - - -

      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

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

      Returned (function value):
                    int       status:  0 = OK

      Notes:

      1) 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.

      2) 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.

      3) TDB is essentially the same as Teph, the time argument for the
         JPL solar system ephemerides.

      References:

         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

      Copyright (C) 2013-2023, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.