src/Marando/IAU/iauGst00a.php
public static function Gst00a($uta, $utb, $tta, $ttb) {
    $gmst00;
    $ee00a;
    $gst;

    $gmst00 = IAU::Gmst00($uta, $utb, $tta, $ttb);
    $ee00a  = IAU::Ee00a($tta, $ttb);
    $gst    = IAU::Anp($gmst00 + $ee00a);

    return $gst;
  }
public static function Gst00a($uta, $utb, $tta, $ttb) {
    $gmst00;
    $ee00a;
    $gst;

    $gmst00 = IAU::Gmst00($uta, $utb, $tta, $ttb);
    $ee00a  = IAU::Ee00a($tta, $ttb);
    $gst    = IAU::Anp($gmst00 + $ee00a);

    return $gst;
  }
public static function Gst00a ( $ uta , $ utb , $ tta , $ ttb ) { $ gmst00 ; $ ee00a ; $ gst ; $ gmst00 = IAU :: Gmst00 ( $ uta , $ utb , $ tta , $ ttb ) ; $ ee00a = IAU :: Ee00a ( $ tta , $ ttb ) ; $ gst = IAU :: Anp ( $ gmst00 + $ ee00a ) ; return $ gst ; }
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i a u G s t 0 0 a
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Greenwich apparent sidereal time (consistent with IAU 2000
resolutions).

This function is part of the International Astronomical Union's
SOFA (Standards Of Fundamental Astronomy) software collection.

Status:  canonical model.

Given:
uta,utb    double    UT1 as a 2-part Julian Date (Notes 1,2)
tta,ttb    double    TT as a 2-part Julian Date (Notes 1,2)

Returned (function value):
double    Greenwich apparent sidereal time (radians)

Notes:

1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
Julian Dates, apportioned in any convenient way between the
argument pairs.  For example, JD=2450123.7 could be expressed in
any of these ways, among others:

Part A        Part B

2450123.7           0.0       (JD method)
2451545.0       -1421.3       (J2000 method)
2400000.5       50123.2       (MJD method)
2450123.5           0.2       (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 (in the case of UT;  the TT is not at all critical
in this respect).  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 function, called internally:  maximum precision 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) Both UT1 and TT are required, UT1 to predict the Earth rotation
and TT to predict the effects of precession-nutation.  If UT1 is
used for both purposes, errors of order 100 microarcseconds
result.

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:
iauGmst00    Greenwich mean sidereal time, IAU 2000
iauEe00a     equation of the equinoxes, IAU 2000A
iauAnp       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., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)

This revision:  2013 June 18

SOFA release 2015-02-09

Copyright (C) 2015 IAU SOFA Board.  See notes at end.
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