/measures/fortran/sofa/gst00a.f
FORTRAN Legacy | 173 lines | 7 code | 8 blank | 158 comment | 0 complexity | 4b67c08c004b6e3de65e3a8648edfbf8 MD5 | raw file
Possible License(s): GPL-2.0
- DOUBLE PRECISION FUNCTION iau_GST00A ( UTA, UTB, TTA, TTB )
- *+
- * - - - - - - - - - - -
- * i a u _ G S T 0 0 A
- * - - - - - - - - - - -
- *
- * Greenwich Apparent Sidereal Time (consistent with IAU 2000
- * resolutions).
- *
- * This routine is part of the International Astronomical Union's
- * SOFA (Standards of Fundamental Astronomy) software collection.
- *
- * Status: canonical model.
- *
- * Given:
- * UTA, UTB d UT1 as a 2-part Julian Date (Notes 1,2)
- * TTA, TTB d TT as a 2-part Julian Date (Notes 1,2)
- *
- * The result is the Greenwich Apparent Sidereal Time (radians), in the
- * range 0 to 2pi.
- *
- * 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
- *
- * 2450123.7D0 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 (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 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) 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 algorithm is from Capitaine et al. (2003) and IERS Conventions
- * 2003.
- *
- * Called:
- * iau_GMST00 Greenwich Mean Sidereal Time, IAU 2000
- * iau_EE00A equation of the equinoxes, IAU 2000A
- * 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., Petit, G. (eds.), IERS Conventions (2003),
- * IERS Technical Note No. 32, BKG (2004)
- *
- * This revision: 2005 August 24
- *
- * Copyright (C) 2005 IAU SOFA Review Board. See notes at end.
- *
- *-----------------------------------------------------------------------
- IMPLICIT NONE
- DOUBLE PRECISION UTA, UTB, TTA, TTB
- DOUBLE PRECISION iau_ANP, iau_GMST00, iau_EE00A
- * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- iau_GST00A = iau_ANP ( iau_GMST00 ( UTA,UTB, TTA,TTB ) +
- : iau_EE00A ( TTA,TTB ) )
- * Finished.
- *+----------------------------------------------------------------------
- *
- * Copyright (C) 2005
- * 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. The Software is made available free of charge for use by:
- *
- * a) private individuals for non-profit research; and
- *
- * b) non-profit educational, academic and research institutions.
- *
- * 3. Commercial use of the Software is specifically excluded from the
- * terms and conditions of this license. Commercial use of the
- * Software is subject to the prior written agreement of the Board on
- * terms to be agreed.
- *
- * 4. The provision of any version of the 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.
- *
- * 5. The user may modify the Software for his/her own purposes. The
- * user may distribute the modified software provided that the Board
- * is informed and that a copy of the modified software is made
- * available to the Board on request. All modifications made by the
- * user shall be clearly identified to show how the modified software
- * differs from the original Software, and the name(s) of the
- * affected routine(s) shall be changed. The original SOFA Software
- * License text must be present.
- *
- * 6. In any published work produced by the user and which includes
- * results achieved by using the Software, the user shall acknowledge
- * that the Software was used in producing the information contained
- * in such publication.
- *
- * 7. The user may incorporate or embed the Software into other software
- * products which he/she may then give away free of charge but not
- * sell provided the user makes due acknowledgement of the use which
- * he/she has made of the Software in creating such software
- * products. Any redistribution of the Software in this way shall be
- * made under the same terms and conditions under which the user
- * received it from the SOFA Center.
- *
- * 8. The user shall not cause the Software to be brought into
- * disrepute, either by misuse, or use for inappropriate tasks, or by
- * inappropriate modification.
- *
- * 9. The Software is provided to the user "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 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.
- *
- * 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
- *
- *
- *-----------------------------------------------------------------------
- END