source: trunk/FACT++/sofa/src/ee00b.c@ 18368

Last change on this file since 18368 was 18346, checked in by tbretz, 11 years ago
File size: 7.3 KB
Line 
1#include "sofa.h"
2
3double iauEe00b(double date1, double date2)
4/*
5** - - - - - - - - -
6** i a u 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** This function is part of the International Astronomical Union's
13** SOFA (Standards Of Fundamental Astronomy) software collection.
14**
15** Status: support function.
16**
17** Given:
18** date1,date2 double TT as a 2-part Julian Date (Note 1)
19**
20** Returned (function value):
21** double equation of the equinoxes (Note 2)
22**
23** Notes:
24**
25** 1) The TT date date1+date2 is a Julian Date, apportioned in any
26** convenient way between the two arguments. For example,
27** JD(TT)=2450123.7 could be expressed in any of these ways,
28** among others:
29**
30** date1 date2
31**
32** 2450123.7 0.0 (JD method)
33** 2451545.0 -1421.3 (J2000 method)
34** 2400000.5 50123.2 (MJD method)
35** 2450123.5 0.2 (date & time method)
36**
37** The JD method is the most natural and convenient to use in
38** cases where the loss of several decimal digits of resolution
39** is acceptable. The J2000 method is best matched to the way
40** the argument is handled internally and will deliver the
41** optimum resolution. The MJD method and the date & time methods
42** are both good compromises between resolution and convenience.
43**
44** 2) The result, which is in radians, operates in the following sense:
45**
46** Greenwich apparent ST = GMST + equation of the equinoxes
47**
48** 3) The result is compatible with the IAU 2000 resolutions except
49** that accuracy has been compromised for the sake of speed. For
50** further details, see McCarthy & Luzum (2001), IERS Conventions
51** 2003 and Capitaine et al. (2003).
52**
53** Called:
54** iauPr00 IAU 2000 precession adjustments
55** iauObl80 mean obliquity, IAU 1980
56** iauNut00b nutation, IAU 2000B
57** iauEe00 equation of the equinoxes, IAU 2000
58**
59** References:
60**
61** Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
62** implement the IAU 2000 definition of UT1", Astronomy &
63** Astrophysics, 406, 1135-1149 (2003)
64**
65** McCarthy, D.D. & Luzum, B.J., "An abridged model of the
66** precession-nutation of the celestial pole", Celestial Mechanics &
67** Dynamical Astronomy, 85, 37-49 (2003)
68**
69** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
70** IERS Technical Note No. 32, BKG (2004)
71**
72** This revision: 2008 May 18
73**
74** SOFA release 2015-02-09
75**
76** Copyright (C) 2015 IAU SOFA Board. See notes at end.
77*/
78{
79 double dpsipr, depspr, epsa, dpsi, deps, ee;
80
81/* IAU 2000 precession-rate adjustments. */
82 iauPr00(date1, date2, &dpsipr, &depspr);
83
84/* Mean obliquity, consistent with IAU 2000 precession-nutation. */
85 epsa = iauObl80(date1, date2) + depspr;
86
87/* Nutation in longitude. */
88 iauNut00b(date1, date2, &dpsi, &deps);
89
90/* Equation of the equinoxes. */
91 ee = iauEe00(date1, date2, epsa, dpsi);
92
93 return ee;
94
95/*----------------------------------------------------------------------
96**
97** Copyright (C) 2015
98** Standards Of Fundamental Astronomy Board
99** of the International Astronomical Union.
100**
101** =====================
102** SOFA Software License
103** =====================
104**
105** NOTICE TO USER:
106**
107** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
108** CONDITIONS WHICH APPLY TO ITS USE.
109**
110** 1. The Software is owned by the IAU SOFA Board ("SOFA").
111**
112** 2. Permission is granted to anyone to use the SOFA software for any
113** purpose, including commercial applications, free of charge and
114** without payment of royalties, subject to the conditions and
115** restrictions listed below.
116**
117** 3. You (the user) may copy and distribute SOFA source code to others,
118** and use and adapt its code and algorithms in your own software,
119** on a world-wide, royalty-free basis. That portion of your
120** distribution that does not consist of intact and unchanged copies
121** of SOFA source code files is a "derived work" that must comply
122** with the following requirements:
123**
124** a) Your work shall be marked or carry a statement that it
125** (i) uses routines and computations derived by you from
126** software provided by SOFA under license to you; and
127** (ii) does not itself constitute software provided by and/or
128** endorsed by SOFA.
129**
130** b) The source code of your derived work must contain descriptions
131** of how the derived work is based upon, contains and/or differs
132** from the original SOFA software.
133**
134** c) The names of all routines in your derived work shall not
135** include the prefix "iau" or "sofa" or trivial modifications
136** thereof such as changes of case.
137**
138** d) The origin of the SOFA components of your derived work must
139** not be misrepresented; you must not claim that you wrote the
140** original software, nor file a patent application for SOFA
141** software or algorithms embedded in the SOFA software.
142**
143** e) These requirements must be reproduced intact in any source
144** distribution and shall apply to anyone to whom you have
145** granted a further right to modify the source code of your
146** derived work.
147**
148** Note that, as originally distributed, the SOFA software is
149** intended to be a definitive implementation of the IAU standards,
150** and consequently third-party modifications are discouraged. All
151** variations, no matter how minor, must be explicitly marked as
152** such, as explained above.
153**
154** 4. You shall not cause the SOFA software to be brought into
155** disrepute, either by misuse, or use for inappropriate tasks, or
156** by inappropriate modification.
157**
158** 5. The SOFA software is provided "as is" and SOFA makes no warranty
159** as to its use or performance. SOFA does not and cannot warrant
160** the performance or results which the user may obtain by using the
161** SOFA software. SOFA makes no warranties, express or implied, as
162** to non-infringement of third party rights, merchantability, or
163** fitness for any particular purpose. In no event will SOFA be
164** liable to the user for any consequential, incidental, or special
165** damages, including any lost profits or lost savings, even if a
166** SOFA representative has been advised of such damages, or for any
167** claim by any third party.
168**
169** 6. The provision of any version of the SOFA software under the terms
170** and conditions specified herein does not imply that future
171** versions will also be made available under the same terms and
172** conditions.
173*
174** In any published work or commercial product which uses the SOFA
175** software directly, acknowledgement (see www.iausofa.org) is
176** appreciated.
177**
178** Correspondence concerning SOFA software should be addressed as
179** follows:
180**
181** By email: sofa@ukho.gov.uk
182** By post: IAU SOFA Center
183** HM Nautical Almanac Office
184** UK Hydrographic Office
185** Admiralty Way, Taunton
186** Somerset, TA1 2DN
187** United Kingdom
188**
189**--------------------------------------------------------------------*/
190}
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