source: trunk/FACT++/sofa/src/ee00a.c@ 18365

Last change on this file since 18365 was 18346, checked in by tbretz, 10 years ago
File size: 6.9 KB
Line 
1#include "sofa.h"
2
3double iauEe00a(double date1, double date2)
4/*
5** - - - - - - - - -
6** i a u E e 0 0 a
7** - - - - - - - - -
8**
9** Equation of the equinoxes, compatible with IAU 2000 resolutions.
10**
11** This function is part of the International Astronomical Union's
12** SOFA (Standards Of Fundamental Astronomy) software collection.
13**
14** Status: support function.
15**
16** Given:
17** date1,date2 double TT as a 2-part Julian Date (Note 1)
18**
19** Returned (function value):
20** double equation of the equinoxes (Note 2)
21**
22** Notes:
23**
24** 1) The TT date date1+date2 is a Julian Date, apportioned in any
25** convenient way between the two arguments. For example,
26** JD(TT)=2450123.7 could be expressed in any of these ways,
27** among others:
28**
29** date1 date2
30**
31** 2450123.7 0.0 (JD method)
32** 2451545.0 -1421.3 (J2000 method)
33** 2400000.5 50123.2 (MJD method)
34** 2450123.5 0.2 (date & time method)
35**
36** The JD method is the most natural and convenient to use in
37** cases where the loss of several decimal digits of resolution
38** is acceptable. The J2000 method is best matched to the way
39** the argument is handled internally and will deliver the
40** optimum resolution. The MJD method and the date & time methods
41** are both good compromises between resolution and convenience.
42**
43** 2) The result, which is in radians, operates in the following sense:
44**
45** Greenwich apparent ST = GMST + equation of the equinoxes
46**
47** 3) The result is compatible with the IAU 2000 resolutions. For
48** further details, see IERS Conventions 2003 and Capitaine et al.
49** (2002).
50**
51** Called:
52** iauPr00 IAU 2000 precession adjustments
53** iauObl80 mean obliquity, IAU 1980
54** iauNut00a nutation, IAU 2000A
55** iauEe00 equation of the equinoxes, IAU 2000
56**
57** References:
58**
59** Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
60** implement the IAU 2000 definition of UT1", Astronomy &
61** Astrophysics, 406, 1135-1149 (2003).
62**
63** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
64** IERS Technical Note No. 32, BKG (2004).
65**
66** This revision: 2008 May 16
67**
68** SOFA release 2015-02-09
69**
70** Copyright (C) 2015 IAU SOFA Board. See notes at end.
71*/
72{
73 double dpsipr, depspr, epsa, dpsi, deps, ee;
74
75/* IAU 2000 precession-rate adjustments. */
76 iauPr00(date1, date2, &dpsipr, &depspr);
77
78/* Mean obliquity, consistent with IAU 2000 precession-nutation. */
79 epsa = iauObl80(date1, date2) + depspr;
80
81/* Nutation in longitude. */
82 iauNut00a(date1, date2, &dpsi, &deps);
83
84/* Equation of the equinoxes. */
85 ee = iauEe00(date1, date2, epsa, dpsi);
86
87 return ee;
88
89/*----------------------------------------------------------------------
90**
91** Copyright (C) 2015
92** Standards Of Fundamental Astronomy Board
93** of the International Astronomical Union.
94**
95** =====================
96** SOFA Software License
97** =====================
98**
99** NOTICE TO USER:
100**
101** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
102** CONDITIONS WHICH APPLY TO ITS USE.
103**
104** 1. The Software is owned by the IAU SOFA Board ("SOFA").
105**
106** 2. Permission is granted to anyone to use the SOFA software for any
107** purpose, including commercial applications, free of charge and
108** without payment of royalties, subject to the conditions and
109** restrictions listed below.
110**
111** 3. You (the user) may copy and distribute SOFA source code to others,
112** and use and adapt its code and algorithms in your own software,
113** on a world-wide, royalty-free basis. That portion of your
114** distribution that does not consist of intact and unchanged copies
115** of SOFA source code files is a "derived work" that must comply
116** with the following requirements:
117**
118** a) Your work shall be marked or carry a statement that it
119** (i) uses routines and computations derived by you from
120** software provided by SOFA under license to you; and
121** (ii) does not itself constitute software provided by and/or
122** endorsed by SOFA.
123**
124** b) The source code of your derived work must contain descriptions
125** of how the derived work is based upon, contains and/or differs
126** from the original SOFA software.
127**
128** c) The names of all routines in your derived work shall not
129** include the prefix "iau" or "sofa" or trivial modifications
130** thereof such as changes of case.
131**
132** d) The origin of the SOFA components of your derived work must
133** not be misrepresented; you must not claim that you wrote the
134** original software, nor file a patent application for SOFA
135** software or algorithms embedded in the SOFA software.
136**
137** e) These requirements must be reproduced intact in any source
138** distribution and shall apply to anyone to whom you have
139** granted a further right to modify the source code of your
140** derived work.
141**
142** Note that, as originally distributed, the SOFA software is
143** intended to be a definitive implementation of the IAU standards,
144** and consequently third-party modifications are discouraged. All
145** variations, no matter how minor, must be explicitly marked as
146** such, as explained above.
147**
148** 4. You shall not cause the SOFA software to be brought into
149** disrepute, either by misuse, or use for inappropriate tasks, or
150** by inappropriate modification.
151**
152** 5. The SOFA software is provided "as is" and SOFA makes no warranty
153** as to its use or performance. SOFA does not and cannot warrant
154** the performance or results which the user may obtain by using the
155** SOFA software. SOFA makes no warranties, express or implied, as
156** to non-infringement of third party rights, merchantability, or
157** fitness for any particular purpose. In no event will SOFA be
158** liable to the user for any consequential, incidental, or special
159** damages, including any lost profits or lost savings, even if a
160** SOFA representative has been advised of such damages, or for any
161** claim by any third party.
162**
163** 6. The provision of any version of the SOFA software under the terms
164** and conditions specified herein does not imply that future
165** versions will also be made available under the same terms and
166** conditions.
167*
168** In any published work or commercial product which uses the SOFA
169** software directly, acknowledgement (see www.iausofa.org) is
170** appreciated.
171**
172** Correspondence concerning SOFA software should be addressed as
173** follows:
174**
175** By email: sofa@ukho.gov.uk
176** By post: IAU SOFA Center
177** HM Nautical Almanac Office
178** UK Hydrographic Office
179** Admiralty Way, Taunton
180** Somerset, TA1 2DN
181** United Kingdom
182**
183**--------------------------------------------------------------------*/
184}
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