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