source: branches/FACT++_lidctrl_usb/erfa/src/ee00a.c@ 19875

Last change on this file since 19875 was 18711, checked in by tbretz, 10 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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