SUBROUTINE iau_TTTDB ( TT1, TT2, DTR, TDB1, TDB2, J )
*+
*  - - - - - - - - - -
*   i a u _ T T T D B
*  - - - - - - - - - -
*
*  Time scale transformation:  Terrestrial Time, TT, to Barycentric
*  Dynamical Time, TDB.
*
*  This routine is part of the International Astronomical Union's
*  SOFA (Standards of Fundamental Astronomy) software collection.
*
*  Status:  canonical.
*
*  Given:
*     TT1,TT2      d      TT as a 2-part Julian Date
*     DTR          d      TDB-TT in seconds
*
*  Returned:
*     TDB1,TDB2    d      TDB as a 2-part Julian Date
*     J            i      status:  0 = OK
*
*  Notes:
*
*  1) TT1+TT2 is Julian Date, apportioned in any convenient way between
*     the two arguments, for example where TT1 is the Julian Day Number
*     and TT2 is the fraction of a day.  The returned TDB1,TDB2 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 SOFA routine
*     iau_DTDB.  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:  2019 June 20
*
*  SOFA release 2023-10-11
*
*  Copyright (C) 2023 IAU SOFA Board.  See notes at end.
*
*-----------------------------------------------------------------------

      IMPLICIT NONE
      DOUBLE PRECISION TT1, TT2, DTR, TDB1, TDB2
      INTEGER J

*  Days to seconds
      DOUBLE PRECISION D2S
      PARAMETER ( D2S = 86400D0 )

      DOUBLE PRECISION DTRD

* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

*  Result, safeguarding precision.
      DTRD = DTR/D2S
      IF ( ABS(TT1).GT.ABS(TT2) ) THEN
         TDB1 = TT1
         TDB2 = TT2 + DTRD
      ELSE
         TDB1 = TT1 + DTRD
         TDB2 = TT2
      END IF

*  Status (always OK).
      J = 0

*  Finished.

*+----------------------------------------------------------------------
*
*  Copyright (C) 2023
*  Standards of Fundamental Astronomy Board
*  of the International Astronomical Union.
*
*  =====================
*  SOFA Software License
*  =====================
*
*  NOTICE TO USER:
*
*  BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
*  CONDITIONS WHICH APPLY TO ITS USE.
*
*  1. The Software is owned by the IAU SOFA Board ("SOFA").
*
*  2. Permission is granted to anyone to use the SOFA software for any
*     purpose, including commercial applications, free of charge and
*     without payment of royalties, subject to the conditions and
*     restrictions listed below.
*
*  3. You (the user) may copy and distribute SOFA source code to others,
*     and use and adapt its code and algorithms in your own software,
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*     distribution that does not consist of intact and unchanged copies
*     of SOFA source code files is a "derived work" that must comply
*     with the following requirements:
*
*     a) Your work shall be marked or carry a statement that it
*        (i) uses routines and computations derived by you from
*        software provided by SOFA under license to you; and
*        (ii) does not itself constitute software provided by and/or
*        endorsed by SOFA.
*
*     b) The source code of your derived work must contain descriptions
*        of how the derived work is based upon, contains and/or differs
*        from the original SOFA software.
*
*     c) The names of all routines in your derived work shall not
*        include the prefix "iau" or "sofa" or trivial modifications
*        thereof such as changes of case.
*
*     d) The origin of the SOFA components of your derived work must
*        not be misrepresented;  you must not claim that you wrote the
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*
*     e) These requirements must be reproduced intact in any source
*        distribution and shall apply to anyone to whom you have
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*
*     Note that, as originally distributed, the SOFA software is
*     intended to be a definitive implementation of the IAU standards,
*     and consequently third-party modifications are discouraged.  All
*     variations, no matter how minor, must be explicitly marked as
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*
*  4. You shall not cause the SOFA software to be brought into
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*
*  5. The SOFA software is provided "as is" and SOFA makes no warranty
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*
*  6. The provision of any version of the SOFA software under the terms
*     and conditions specified herein does not imply that future
*     versions will also be made available under the same terms and
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*
*  In any published work or commercial product which uses the SOFA
*  software directly, acknowledgement (see www.iausofa.org) is
*  appreciated.
*
*  Correspondence concerning SOFA software should be addressed as
*  follows:
*
*      By email:  sofa@ukho.gov.uk
*      By post:   IAU SOFA Center
*                 HM Nautical Almanac Office
*                 UK Hydrographic Office
*                 Admiralty Way, Taunton
*                 Somerset, TA1 2DN
*                 United Kingdom
*
*-----------------------------------------------------------------------

      END