source: trunk/FACT++/sofa/src/ee06a.c@ 18368

Last change on this file since 18368 was 18346, checked in by tbretz, 11 years ago
File size: 6.5 KB
Line 
1#include "sofa.h"
2
3double iauEe06a(double date1, double date2)
4/*
5** - - - - - - - - -
6** i a u E e 0 6 a
7** - - - - - - - - -
8**
9** Equation of the equinoxes, compatible with IAU 2000 resolutions and
10** IAU 2006/2000A precession-nutation.
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** Called:
49** iauAnpm normalize angle into range +/- pi
50** iauGst06a Greenwich apparent sidereal time, IAU 2006/2000A
51** iauGmst06 Greenwich mean sidereal time, IAU 2006
52**
53** Reference:
54**
55** McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
56** IERS Technical Note No. 32, BKG
57**
58** This revision: 2008 May 18
59**
60** SOFA release 2015-02-09
61**
62** Copyright (C) 2015 IAU SOFA Board. See notes at end.
63*/
64{
65 double gst06a, gmst06, ee;
66
67/* Apparent and mean sidereal times. */
68 gst06a = iauGst06a(0.0, 0.0, date1, date2);
69 gmst06 = iauGmst06(0.0, 0.0, date1, date2);
70
71/* Equation of the equinoxes. */
72 ee = iauAnpm(gst06a - gmst06);
73
74 return ee;
75
76/*----------------------------------------------------------------------
77**
78** Copyright (C) 2015
79** Standards Of Fundamental Astronomy Board
80** of the International Astronomical Union.
81**
82** =====================
83** SOFA Software License
84** =====================
85**
86** NOTICE TO USER:
87**
88** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
89** CONDITIONS WHICH APPLY TO ITS USE.
90**
91** 1. The Software is owned by the IAU SOFA Board ("SOFA").
92**
93** 2. Permission is granted to anyone to use the SOFA software for any
94** purpose, including commercial applications, free of charge and
95** without payment of royalties, subject to the conditions and
96** restrictions listed below.
97**
98** 3. You (the user) may copy and distribute SOFA source code to others,
99** and use and adapt its code and algorithms in your own software,
100** on a world-wide, royalty-free basis. That portion of your
101** distribution that does not consist of intact and unchanged copies
102** of SOFA source code files is a "derived work" that must comply
103** with the following requirements:
104**
105** a) Your work shall be marked or carry a statement that it
106** (i) uses routines and computations derived by you from
107** software provided by SOFA under license to you; and
108** (ii) does not itself constitute software provided by and/or
109** endorsed by SOFA.
110**
111** b) The source code of your derived work must contain descriptions
112** of how the derived work is based upon, contains and/or differs
113** from the original SOFA software.
114**
115** c) The names of all routines in your derived work shall not
116** include the prefix "iau" or "sofa" or trivial modifications
117** thereof such as changes of case.
118**
119** d) The origin of the SOFA components of your derived work must
120** not be misrepresented; you must not claim that you wrote the
121** original software, nor file a patent application for SOFA
122** software or algorithms embedded in the SOFA software.
123**
124** e) These requirements must be reproduced intact in any source
125** distribution and shall apply to anyone to whom you have
126** granted a further right to modify the source code of your
127** derived work.
128**
129** Note that, as originally distributed, the SOFA software is
130** intended to be a definitive implementation of the IAU standards,
131** and consequently third-party modifications are discouraged. All
132** variations, no matter how minor, must be explicitly marked as
133** such, as explained above.
134**
135** 4. You shall not cause the SOFA software to be brought into
136** disrepute, either by misuse, or use for inappropriate tasks, or
137** by inappropriate modification.
138**
139** 5. The SOFA software is provided "as is" and SOFA makes no warranty
140** as to its use or performance. SOFA does not and cannot warrant
141** the performance or results which the user may obtain by using the
142** SOFA software. SOFA makes no warranties, express or implied, as
143** to non-infringement of third party rights, merchantability, or
144** fitness for any particular purpose. In no event will SOFA be
145** liable to the user for any consequential, incidental, or special
146** damages, including any lost profits or lost savings, even if a
147** SOFA representative has been advised of such damages, or for any
148** claim by any third party.
149**
150** 6. The provision of any version of the SOFA software under the terms
151** and conditions specified herein does not imply that future
152** versions will also be made available under the same terms and
153** conditions.
154*
155** In any published work or commercial product which uses the SOFA
156** software directly, acknowledgement (see www.iausofa.org) is
157** appreciated.
158**
159** Correspondence concerning SOFA software should be addressed as
160** follows:
161**
162** By email: sofa@ukho.gov.uk
163** By post: IAU SOFA Center
164** HM Nautical Almanac Office
165** UK Hydrographic Office
166** Admiralty Way, Taunton
167** Somerset, TA1 2DN
168** United Kingdom
169**
170**--------------------------------------------------------------------*/
171}
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