source: branches/FACT++_part_filenames/erfa/src/ee06a.c@ 19365

Last change on this file since 19365 was 18711, checked in by tbretz, 8 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 5.0 KB
Line 
1#include "erfa.h"
2
3double eraEe06a(double date1, double date2)
4/*
5** - - - - - - - - -
6** e r a E e 0 6 a
7** - - - - - - - - -
8**
9** Equation of the equinoxes, compatible with IAU 2000 resolutions and
10** IAU 2006/2000A precession-nutation.
11**
12** Given:
13** date1,date2 double TT as a 2-part Julian Date (Note 1)
14**
15** Returned (function value):
16** double equation of the equinoxes (Note 2)
17**
18** Notes:
19**
20** 1) The TT date date1+date2 is a Julian Date, apportioned in any
21** convenient way between the two arguments. For example,
22** JD(TT)=2450123.7 could be expressed in any of these ways,
23** among others:
24**
25** date1 date2
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. The J2000 method is best matched to the way
35** the argument is handled internally and will deliver the
36** optimum resolution. The MJD method and the date & time methods
37** are both good compromises between resolution and convenience.
38**
39** 2) The result, which is in radians, operates in the following sense:
40**
41** Greenwich apparent ST = GMST + equation of the equinoxes
42**
43** Called:
44** eraAnpm normalize angle into range +/- pi
45** eraGst06a Greenwich apparent sidereal time, IAU 2006/2000A
46** eraGmst06 Greenwich mean sidereal time, IAU 2006
47**
48** Reference:
49**
50** McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
51** IERS Technical Note No. 32, BKG
52**
53** Copyright (C) 2013-2016, NumFOCUS Foundation.
54** Derived, with permission, from the SOFA library. See notes at end of file.
55*/
56{
57 double gst06a, gmst06, ee;
58
59
60/* Apparent and mean sidereal times. */
61 gst06a = eraGst06a(0.0, 0.0, date1, date2);
62 gmst06 = eraGmst06(0.0, 0.0, date1, date2);
63
64/* Equation of the equinoxes. */
65 ee = eraAnpm(gst06a - gmst06);
66
67 return ee;
68
69}
70/*----------------------------------------------------------------------
71**
72**
73** Copyright (C) 2013-2016, NumFOCUS Foundation.
74** All rights reserved.
75**
76** This library is derived, with permission, from the International
77** Astronomical Union's "Standards of Fundamental Astronomy" library,
78** available from http://www.iausofa.org.
79**
80** The ERFA version is intended to retain identical functionality to
81** the SOFA library, but made distinct through different function and
82** file names, as set out in the SOFA license conditions. The SOFA
83** original has a role as a reference standard for the IAU and IERS,
84** and consequently redistribution is permitted only in its unaltered
85** state. The ERFA version is not subject to this restriction and
86** therefore can be included in distributions which do not support the
87** concept of "read only" software.
88**
89** Although the intent is to replicate the SOFA API (other than
90** replacement of prefix names) and results (with the exception of
91** bugs; any that are discovered will be fixed), SOFA is not
92** responsible for any errors found in this version of the library.
93**
94** If you wish to acknowledge the SOFA heritage, please acknowledge
95** that you are using a library derived from SOFA, rather than SOFA
96** itself.
97**
98**
99** TERMS AND CONDITIONS
100**
101** Redistribution and use in source and binary forms, with or without
102** modification, are permitted provided that the following conditions
103** are met:
104**
105** 1 Redistributions of source code must retain the above copyright
106** notice, this list of conditions and the following disclaimer.
107**
108** 2 Redistributions in binary form must reproduce the above copyright
109** notice, this list of conditions and the following disclaimer in
110** the documentation and/or other materials provided with the
111** distribution.
112**
113** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
114** the International Astronomical Union nor the names of its
115** contributors may be used to endorse or promote products derived
116** from this software without specific prior written permission.
117**
118** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
119** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
120** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
121** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
122** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
123** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
124** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
125** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
126** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
127** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
128** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
129** POSSIBILITY OF SUCH DAMAGE.
130**
131*/
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