1 #include "sofa.h"
2
iauEe00b(double date1,double date2)3 double 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 (1 mas) for the sake of speed.
50 ** For further details, see McCarthy & Luzum (2003), IERS
51 ** Conventions 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: 2021 May 11
73 **
74 ** SOFA release 2021-05-12
75 **
76 ** Copyright (C) 2021 IAU SOFA Board. See notes at end.
77 */
78 {
79 double dpsipr, depspr, epsa, dpsi, deps, ee;
80
81
82 /* IAU 2000 precession-rate adjustments. */
83 iauPr00(date1, date2, &dpsipr, &depspr);
84
85 /* Mean obliquity, consistent with IAU 2000 precession-nutation. */
86 epsa = iauObl80(date1, date2) + depspr;
87
88 /* Nutation in longitude. */
89 iauNut00b(date1, date2, &dpsi, &deps);
90
91 /* Equation of the equinoxes. */
92 ee = iauEe00(date1, date2, epsa, dpsi);
93
94 return ee;
95
96 /* Finished. */
97
98 /*----------------------------------------------------------------------
99 **
100 ** Copyright (C) 2021
101 ** Standards Of Fundamental Astronomy Board
102 ** of the International Astronomical Union.
103 **
104 ** =====================
105 ** SOFA Software License
106 ** =====================
107 **
108 ** NOTICE TO USER:
109 **
110 ** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
111 ** CONDITIONS WHICH APPLY TO ITS USE.
112 **
113 ** 1. The Software is owned by the IAU SOFA Board ("SOFA").
114 **
115 ** 2. Permission is granted to anyone to use the SOFA software for any
116 ** purpose, including commercial applications, free of charge and
117 ** without payment of royalties, subject to the conditions and
118 ** restrictions listed below.
119 **
120 ** 3. You (the user) may copy and distribute SOFA source code to others,
121 ** and use and adapt its code and algorithms in your own software,
122 ** on a world-wide, royalty-free basis. That portion of your
123 ** distribution that does not consist of intact and unchanged copies
124 ** of SOFA source code files is a "derived work" that must comply
125 ** with the following requirements:
126 **
127 ** a) Your work shall be marked or carry a statement that it
128 ** (i) uses routines and computations derived by you from
129 ** software provided by SOFA under license to you; and
130 ** (ii) does not itself constitute software provided by and/or
131 ** endorsed by SOFA.
132 **
133 ** b) The source code of your derived work must contain descriptions
134 ** of how the derived work is based upon, contains and/or differs
135 ** from the original SOFA software.
136 **
137 ** c) The names of all routines in your derived work shall not
138 ** include the prefix "iau" or "sofa" or trivial modifications
139 ** thereof such as changes of case.
140 **
141 ** d) The origin of the SOFA components of your derived work must
142 ** not be misrepresented; you must not claim that you wrote the
143 ** original software, nor file a patent application for SOFA
144 ** software or algorithms embedded in the SOFA software.
145 **
146 ** e) These requirements must be reproduced intact in any source
147 ** distribution and shall apply to anyone to whom you have
148 ** granted a further right to modify the source code of your
149 ** derived work.
150 **
151 ** Note that, as originally distributed, the SOFA software is
152 ** intended to be a definitive implementation of the IAU standards,
153 ** and consequently third-party modifications are discouraged. All
154 ** variations, no matter how minor, must be explicitly marked as
155 ** such, as explained above.
156 **
157 ** 4. You shall not cause the SOFA software to be brought into
158 ** disrepute, either by misuse, or use for inappropriate tasks, or
159 ** by inappropriate modification.
160 **
161 ** 5. The SOFA software is provided "as is" and SOFA makes no warranty
162 ** as to its use or performance. SOFA does not and cannot warrant
163 ** the performance or results which the user may obtain by using the
164 ** SOFA software. SOFA makes no warranties, express or implied, as
165 ** to non-infringement of third party rights, merchantability, or
166 ** fitness for any particular purpose. In no event will SOFA be
167 ** liable to the user for any consequential, incidental, or special
168 ** damages, including any lost profits or lost savings, even if a
169 ** SOFA representative has been advised of such damages, or for any
170 ** claim by any third party.
171 **
172 ** 6. The provision of any version of the SOFA software under the terms
173 ** and conditions specified herein does not imply that future
174 ** versions will also be made available under the same terms and
175 ** conditions.
176 *
177 ** In any published work or commercial product which uses the SOFA
178 ** software directly, acknowledgement (see www.iausofa.org) is
179 ** appreciated.
180 **
181 ** Correspondence concerning SOFA software should be addressed as
182 ** follows:
183 **
184 ** By email: sofa@ukho.gov.uk
185 ** By post: IAU SOFA Center
186 ** HM Nautical Almanac Office
187 ** UK Hydrographic Office
188 ** Admiralty Way, Taunton
189 ** Somerset, TA1 2DN
190 ** United Kingdom
191 **
192 **--------------------------------------------------------------------*/
193 }
194