DOUBLE PRECISION FUNCTION iau_GST00B ( UTA, UTB )
*+
*  - - - - - - - - - - -
*   i a u _ G S T 0 0 B
*  - - - - - - - - - - -
*
*  Greenwich Apparent Sidereal Time (consistent with IAU 2000
*  resolutions but using the truncated nutation model IAU 2000B).
*
*  This routine is part of the International Astronomical Union's
*  SOFA (Standards of Fundamental Astronomy) software collection.
*
*  Status:  support routine.
*
*  Given:
*     UTA,UTB      d      UT1 as a 2-part Julian Date (Notes 1,2)
*
*  Returned:
*     iau_GST00B   d      Greenwich apparent sidereal time (radians)
*
*  Notes:
*
*  1) The UT1 date UTA+UTB is a Julian Date, apportioned in any
*     convenient way between the argument pair.  For example,
*     JD(UT1)=2450123.7 could be expressed in any of these ways, among
*     others:
*
*             UTA            UTB
*
*         2450123.7D0        0D0        (JD method)
*          2451545D0      -1421.3D0     (J2000 method)
*         2400000.5D0     50123.2D0     (MJD method)
*         2450123.5D0       0.2D0       (date & time method)
*
*     The JD method is the most natural and convenient to use in cases
*     where the loss of several decimal digits of resolution is
*     acceptable.  The J2000 and MJD methods are good compromises
*     between resolution and convenience.  For UT, the date & time
*     method is best matched to the algorithm that is used by the Earth
*     Rotation Angle routine, called internally:  maximum accuracy (or,
*     at least, minimum noise) is delivered when the UTA argument is for
*     0hrs UT1 on the day in question and the UTB argument lies in the
*     range 0 to 1, or vice versa.
*
*  2) The result is compatible with the IAU 2000 resolutions, except
*     that accuracy has been compromised for the sake of speed and
*     convenience in two respects:
*
*     . UT is used instead of TDB (or TT) to compute the precession
*       component of GMST and the equation of the equinoxes.  This
*       results in errors of order 0.1 mas at present.
*
*     . The IAU 2000B abridged nutation model (McCarthy & Luzum, 2003)
*       is used, introducing errors of up to 1 mas.
*
*  3) This GAST is compatible with the IAU 2000 resolutions and must be
*     used only in conjunction with other IAU 2000 compatible components
*     such as precession-nutation.
*
*  4) The result is returned in the range 0 to 2pi.
*
*  5) The algorithm is from Capitaine et al. (2003) and IERS Conventions
*     2003.
*
*  Called:
*     iau_GMST00   Greenwich mean sidereal time, IAU 2000
*     iau_EE00B    equation of the equinoxes, IAU 2000B
*     iau_ANP      normalize angle into range 0 to 2pi
*
*  References:
*
*     Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
*     implement the IAU 2000 definition of UT1", Astronomy &
*     Astrophysics, 406, 1135-1149 (2003)
*
*     McCarthy, D.D. & Luzum, B.J., "An abridged model of the
*     precession-nutation of the celestial pole", Celestial Mechanics &
*     Dynamical Astronomy, 85, 37-49 (2003)
*
*     McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
*     IERS Technical Note No. 32, BKG (2004)
*
*  This revision:  2020 November 19
*
*  SOFA release 2023-10-11
*
*  Copyright (C) 2023 IAU SOFA Board.  See notes at end.
*
*-----------------------------------------------------------------------

      IMPLICIT NONE

      DOUBLE PRECISION UTA, UTB

      DOUBLE PRECISION iau_ANP, iau_GMST00, iau_EE00B

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

      iau_GST00B = iau_ANP ( iau_GMST00 ( UTA,UTB, UTA,UTB ) +
     :                       iau_EE00B ( UTA,UTB ) )

*  Finished.

*+----------------------------------------------------------------------
*
*  Copyright (C) 2023
*  Standards of Fundamental Astronomy Board
*  of the International Astronomical Union.
*
*  =====================
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*  =====================
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*-----------------------------------------------------------------------

      END