source: trunk/FACT++/erfa/src/ee00b.c@ 18403

Last change on this file since 18403 was 18348, checked in by tbretz, 9 years ago
File size: 5.8 KB
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1#include "erfa.h"
2
3double eraEe00b(double date1, double date2)
4/*
5** - - - - - - - - -
6** e r a E e 0 0 b
7** - - - - - - - - -
8**
9** Equation of the equinoxes, compatible with IAU 2000 resolutions but
10** using the truncated nutation model IAU 2000B.
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** 3) The result is compatible with the IAU 2000 resolutions except
44** that accuracy has been compromised for the sake of speed. For
45** further details, see McCarthy & Luzum (2001), IERS Conventions
46** 2003 and Capitaine et al. (2003).
47**
48** Called:
49** eraPr00 IAU 2000 precession adjustments
50** eraObl80 mean obliquity, IAU 1980
51** eraNut00b nutation, IAU 2000B
52** eraEe00 equation of the equinoxes, IAU 2000
53**
54** References:
55**
56** Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
57** implement the IAU 2000 definition of UT1", Astronomy &
58** Astrophysics, 406, 1135-1149 (2003)
59**
60** McCarthy, D.D. & Luzum, B.J., "An abridged model of the
61** precession-nutation of the celestial pole", Celestial Mechanics &
62** Dynamical Astronomy, 85, 37-49 (2003)
63**
64** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
65** IERS Technical Note No. 32, BKG (2004)
66**
67** Copyright (C) 2013-2015, NumFOCUS Foundation.
68** Derived, with permission, from the SOFA library. See notes at end of file.
69*/
70{
71 double dpsipr, depspr, epsa, dpsi, deps, ee;
72
73/* IAU 2000 precession-rate adjustments. */
74 eraPr00(date1, date2, &dpsipr, &depspr);
75
76/* Mean obliquity, consistent with IAU 2000 precession-nutation. */
77 epsa = eraObl80(date1, date2) + depspr;
78
79/* Nutation in longitude. */
80 eraNut00b(date1, date2, &dpsi, &deps);
81
82/* Equation of the equinoxes. */
83 ee = eraEe00(date1, date2, epsa, dpsi);
84
85 return ee;
86
87}
88/*----------------------------------------------------------------------
89**
90**
91** Copyright (C) 2013-2015, NumFOCUS Foundation.
92** All rights reserved.
93**
94** This library is derived, with permission, from the International
95** Astronomical Union's "Standards of Fundamental Astronomy" library,
96** available from http://www.iausofa.org.
97**
98** The ERFA version is intended to retain identical functionality to
99** the SOFA library, but made distinct through different function and
100** file names, as set out in the SOFA license conditions. The SOFA
101** original has a role as a reference standard for the IAU and IERS,
102** and consequently redistribution is permitted only in its unaltered
103** state. The ERFA version is not subject to this restriction and
104** therefore can be included in distributions which do not support the
105** concept of "read only" software.
106**
107** Although the intent is to replicate the SOFA API (other than
108** replacement of prefix names) and results (with the exception of
109** bugs; any that are discovered will be fixed), SOFA is not
110** responsible for any errors found in this version of the library.
111**
112** If you wish to acknowledge the SOFA heritage, please acknowledge
113** that you are using a library derived from SOFA, rather than SOFA
114** itself.
115**
116**
117** TERMS AND CONDITIONS
118**
119** Redistribution and use in source and binary forms, with or without
120** modification, are permitted provided that the following conditions
121** are met:
122**
123** 1 Redistributions of source code must retain the above copyright
124** notice, this list of conditions and the following disclaimer.
125**
126** 2 Redistributions in binary form must reproduce the above copyright
127** notice, this list of conditions and the following disclaimer in
128** the documentation and/or other materials provided with the
129** distribution.
130**
131** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
132** the International Astronomical Union nor the names of its
133** contributors may be used to endorse or promote products derived
134** from this software without specific prior written permission.
135**
136** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
137** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
138** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
139** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
140** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
141** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
142** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
143** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
144** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
145** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
146** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
147** POSSIBILITY OF SUCH DAMAGE.
148**
149*/
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