source: trunk/FACT++/erfa/src/gmst06.c@ 18367

Last change on this file since 18367 was 18348, checked in by tbretz, 9 years ago
File size: 5.8 KB
Line 
1#include "erfa.h"
2
3double eraGmst06(double uta, double utb, double tta, double ttb)
4/*
5** - - - - - - - - - -
6** e r a G m s t 0 6
7** - - - - - - - - - -
8**
9** Greenwich mean sidereal time (consistent with IAU 2006 precession).
10**
11** Given:
12** uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
13** tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
14**
15** Returned (function value):
16** double Greenwich mean sidereal time (radians)
17**
18** Notes:
19**
20** 1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
21** Julian Dates, apportioned in any convenient way between the
22** argument pairs. For example, JD=2450123.7 could be expressed in
23** any of these ways, among others:
24**
25** Part A Part B
26**
27** 2450123.7 0.0 (JD method)
28** 2451545.0 -1421.3 (J2000 method)
29** 2400000.5 50123.2 (MJD method)
30** 2450123.5 0.2 (date & time method)
31**
32** The JD method is the most natural and convenient to use in
33** cases where the loss of several decimal digits of resolution
34** is acceptable (in the case of UT; the TT is not at all critical
35** in this respect). The J2000 and MJD methods are good compromises
36** between resolution and convenience. For UT, the date & time
37** method is best matched to the algorithm that is used by the Earth
38** rotation angle function, called internally: maximum precision is
39** delivered when the uta argument is for 0hrs UT1 on the day in
40** question and the utb argument lies in the range 0 to 1, or vice
41** versa.
42**
43** 2) Both UT1 and TT are required, UT1 to predict the Earth rotation
44** and TT to predict the effects of precession. If UT1 is used for
45** both purposes, errors of order 100 microarcseconds result.
46**
47** 3) This GMST is compatible with the IAU 2006 precession and must not
48** be used with other precession models.
49**
50** 4) The result is returned in the range 0 to 2pi.
51**
52** Called:
53** eraEra00 Earth rotation angle, IAU 2000
54** eraAnp normalize angle into range 0 to 2pi
55**
56** Reference:
57**
58** Capitaine, N., Wallace, P.T. & Chapront, J., 2005,
59** Astron.Astrophys. 432, 355
60**
61** Copyright (C) 2013-2015, NumFOCUS Foundation.
62** Derived, with permission, from the SOFA library. See notes at end of file.
63*/
64{
65 double t, gmst;
66
67/* TT Julian centuries since J2000.0. */
68 t = ((tta - ERFA_DJ00) + ttb) / ERFA_DJC;
69
70/* Greenwich mean sidereal time, IAU 2006. */
71 gmst = eraAnp(eraEra00(uta, utb) +
72 ( 0.014506 +
73 ( 4612.156534 +
74 ( 1.3915817 +
75 ( -0.00000044 +
76 ( -0.000029956 +
77 ( -0.0000000368 )
78 * t) * t) * t) * t) * t) * ERFA_DAS2R);
79
80 return gmst;
81
82}
83/*----------------------------------------------------------------------
84**
85**
86** Copyright (C) 2013-2015, NumFOCUS Foundation.
87** All rights reserved.
88**
89** This library is derived, with permission, from the International
90** Astronomical Union's "Standards of Fundamental Astronomy" library,
91** available from http://www.iausofa.org.
92**
93** The ERFA version is intended to retain identical functionality to
94** the SOFA library, but made distinct through different function and
95** file names, as set out in the SOFA license conditions. The SOFA
96** original has a role as a reference standard for the IAU and IERS,
97** and consequently redistribution is permitted only in its unaltered
98** state. The ERFA version is not subject to this restriction and
99** therefore can be included in distributions which do not support the
100** concept of "read only" software.
101**
102** Although the intent is to replicate the SOFA API (other than
103** replacement of prefix names) and results (with the exception of
104** bugs; any that are discovered will be fixed), SOFA is not
105** responsible for any errors found in this version of the library.
106**
107** If you wish to acknowledge the SOFA heritage, please acknowledge
108** that you are using a library derived from SOFA, rather than SOFA
109** itself.
110**
111**
112** TERMS AND CONDITIONS
113**
114** Redistribution and use in source and binary forms, with or without
115** modification, are permitted provided that the following conditions
116** are met:
117**
118** 1 Redistributions of source code must retain the above copyright
119** notice, this list of conditions and the following disclaimer.
120**
121** 2 Redistributions in binary form must reproduce the above copyright
122** notice, this list of conditions and the following disclaimer in
123** the documentation and/or other materials provided with the
124** distribution.
125**
126** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
127** the International Astronomical Union nor the names of its
128** contributors may be used to endorse or promote products derived
129** from this software without specific prior written permission.
130**
131** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
132** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
133** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
134** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
135** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
136** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
137** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
138** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
139** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
140** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
141** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
142** POSSIBILITY OF SUCH DAMAGE.
143**
144*/
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