#include "sofam.h"
double iauGmst00(double uta, double utb, double tta, double ttb)
/*
** - - - - - - - - - -
** i a u G m s t 0 0
** - - - - - - - - - -
**
** Greenwich mean sidereal time (model 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 mean 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. If UT1 is used for
** both purposes, errors of order 100 microarcseconds result.
**
** 3) This GMST is compatible with the IAU 2000 resolutions and must be
** used only in conjunction with other IAU 2000 compatible
** components such as precession-nutation and equation of the
** equinoxes.
**
** 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:
** iauEra00 Earth rotation angle, IAU 2000
** 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: 2009 March 16
**
** Copyright (C) 2008 IAU SOFA Review Board. See notes at end.
*/
{
double t, gmst;
/* TT Julian centuries since J2000.0. */
t = ((tta - DJ00) + ttb) / DJC;
/* Greenwich Mean Sidereal Time, IAU 2000. */
gmst = iauAnp(iauEra00(uta, utb) +
( 0.014506 +
( 4612.15739966 +
( 1.39667721 +
( -0.00009344 +
( 0.00001882 )
* t) * t) * t) * t) * DAS2R);
return gmst;
/*-----------------------------------------------------------------------
**
** Copyright (C) 2008
** Standards Of Fundamental Astronomy Review Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS
** WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Review Board ("the Board").
**
** 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 adapt the SOFA software and its
** algorithms for your own purposes and you may copy and distribute
** a resulting "derived work" to others on a world-wide, royalty-free
** basis, provided that the derived work complies 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 contain
** software provided by SOFA or software that has been distributed
** by or endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon and/or differs from the
** original SOFA software.
**
** c) The name(s) of all routine(s) that you distribute shall differ
** from the SOFA names, even when the SOFA content has not been
** otherwise changed.
**
** d) The routine-naming prefix "iau" shall not be used.
**
** e) The origin of the SOFA components of your derived work must not
** be misrepresented; you must not claim that you wrote the
** original software, nor file a patent application for SOFA
** software or algorithms embedded in the SOFA software.
**
** f) These requirements must be reproduced intact in any source
** distribution and shall apply to anyone to whom you have granted
** a further right to modify the source code of your derived work.
**
** 4. In any published work or commercial products which includes
** results achieved by using the SOFA software, you shall acknowledge
** that the SOFA software was used in obtaining those results.
**
** 5. You shall not cause the SOFA software to be brought into
** disrepute, either by misuse, or use for inappropriate tasks, or by
** inappropriate modification.
**
** 6. The SOFA software is provided "as is" and the Board makes no
** warranty as to its use or performance. The Board does not and
** cannot warrant the performance or results which the user may obtain
** by using the SOFA software. The Board makes no warranties, express
** or implied, as to non-infringement of third party rights,
** merchantability, or fitness for any particular purpose. In no
** event will the Board be liable to the user for any consequential,
** incidental, or special damages, including any lost profits or lost
** savings, even if a Board representative has been advised of such
** damages, or for any claim by any third party.
**
** 7. 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
** conditions.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** Internet email: sofa@rl.ac.uk
** Postal address: IAU SOFA Center
** Rutherford Appleton Laboratory
** Chilton, Didcot, Oxon OX11 0QX
** United Kingdom
**
**---------------------------------------------------------------------*/
}