source: trunk/FACT++/erfa/src/ee00a.c@ 18711

Last change on this file since 18711 was 18711, checked in by tbretz, 9 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 5.5 KB
Line 
1#include "erfa.h"
2
3double eraEe00a(double date1, double date2)
4/*
5** - - - - - - - - -
6** e r a E e 0 0 a
7** - - - - - - - - -
8**
9** Equation of the equinoxes, compatible with IAU 2000 resolutions.
10**
11** Given:
12** date1,date2 double TT as a 2-part Julian Date (Note 1)
13**
14** Returned (function value):
15** double equation of the equinoxes (Note 2)
16**
17** Notes:
18**
19** 1) The TT date date1+date2 is a Julian Date, apportioned in any
20** convenient way between the two arguments. For example,
21** JD(TT)=2450123.7 could be expressed in any of these ways,
22** among others:
23**
24** date1 date2
25**
26** 2450123.7 0.0 (JD method)
27** 2451545.0 -1421.3 (J2000 method)
28** 2400000.5 50123.2 (MJD method)
29** 2450123.5 0.2 (date & time method)
30**
31** The JD method is the most natural and convenient to use in
32** cases where the loss of several decimal digits of resolution
33** is acceptable. The J2000 method is best matched to the way
34** the argument is handled internally and will deliver the
35** optimum resolution. The MJD method and the date & time methods
36** are both good compromises between resolution and convenience.
37**
38** 2) The result, which is in radians, operates in the following sense:
39**
40** Greenwich apparent ST = GMST + equation of the equinoxes
41**
42** 3) The result is compatible with the IAU 2000 resolutions. For
43** further details, see IERS Conventions 2003 and Capitaine et al.
44** (2002).
45**
46** Called:
47** eraPr00 IAU 2000 precession adjustments
48** eraObl80 mean obliquity, IAU 1980
49** eraNut00a nutation, IAU 2000A
50** eraEe00 equation of the equinoxes, IAU 2000
51**
52** References:
53**
54** Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
55** implement the IAU 2000 definition of UT1", Astronomy &
56** Astrophysics, 406, 1135-1149 (2003).
57**
58** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
59** IERS Technical Note No. 32, BKG (2004).
60**
61** Copyright (C) 2013-2016, NumFOCUS Foundation.
62** Derived, with permission, from the SOFA library. See notes at end of file.
63*/
64{
65 double dpsipr, depspr, epsa, dpsi, deps, ee;
66
67
68/* IAU 2000 precession-rate adjustments. */
69 eraPr00(date1, date2, &dpsipr, &depspr);
70
71/* Mean obliquity, consistent with IAU 2000 precession-nutation. */
72 epsa = eraObl80(date1, date2) + depspr;
73
74/* Nutation in longitude. */
75 eraNut00a(date1, date2, &dpsi, &deps);
76
77/* Equation of the equinoxes. */
78 ee = eraEe00(date1, date2, epsa, dpsi);
79
80 return ee;
81
82}
83/*----------------------------------------------------------------------
84**
85**
86** Copyright (C) 2013-2016, 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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