1 #include "erfa.h"
2
eraEe00b(double date1,double date2)3 double 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) 2013-2020, 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
74 /* IAU 2000 precession-rate adjustments. */
75 eraPr00(date1, date2, &dpsipr, &depspr);
76
77 /* Mean obliquity, consistent with IAU 2000 precession-nutation. */
78 epsa = eraObl80(date1, date2) + depspr;
79
80 /* Nutation in longitude. */
81 eraNut00b(date1, date2, &dpsi, &deps);
82
83 /* Equation of the equinoxes. */
84 ee = eraEe00(date1, date2, epsa, dpsi);
85
86 return ee;
87
88 }
89 /*----------------------------------------------------------------------
90 **
91 **
92 ** Copyright (C) 2013-2020, NumFOCUS Foundation.
93 ** All rights reserved.
94 **
95 ** This library is derived, with permission, from the International
96 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
97 ** available from http://www.iausofa.org.
98 **
99 ** The ERFA version is intended to retain identical functionality to
100 ** the SOFA library, but made distinct through different function and
101 ** file names, as set out in the SOFA license conditions. The SOFA
102 ** original has a role as a reference standard for the IAU and IERS,
103 ** and consequently redistribution is permitted only in its unaltered
104 ** state. The ERFA version is not subject to this restriction and
105 ** therefore can be included in distributions which do not support the
106 ** concept of "read only" software.
107 **
108 ** Although the intent is to replicate the SOFA API (other than
109 ** replacement of prefix names) and results (with the exception of
110 ** bugs; any that are discovered will be fixed), SOFA is not
111 ** responsible for any errors found in this version of the library.
112 **
113 ** If you wish to acknowledge the SOFA heritage, please acknowledge
114 ** that you are using a library derived from SOFA, rather than SOFA
115 ** itself.
116 **
117 **
118 ** TERMS AND CONDITIONS
119 **
120 ** Redistribution and use in source and binary forms, with or without
121 ** modification, are permitted provided that the following conditions
122 ** are met:
123 **
124 ** 1 Redistributions of source code must retain the above copyright
125 ** notice, this list of conditions and the following disclaimer.
126 **
127 ** 2 Redistributions in binary form must reproduce the above copyright
128 ** notice, this list of conditions and the following disclaimer in
129 ** the documentation and/or other materials provided with the
130 ** distribution.
131 **
132 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
133 ** the International Astronomical Union nor the names of its
134 ** contributors may be used to endorse or promote products derived
135 ** from this software without specific prior written permission.
136 **
137 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
138 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
139 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
140 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
141 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
142 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
143 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
144 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
145 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
146 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
147 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
148 ** POSSIBILITY OF SUCH DAMAGE.
149 **
150 */
151