1 #include "sofa.h"
2 #include "sofam.h"
3
iauPr00(double date1,double date2,double * dpsipr,double * depspr)4 void iauPr00(double date1, double date2, double *dpsipr, double *depspr)
5 /*
6 ** - - - - - - - -
7 ** i a u P r 0 0
8 ** - - - - - - - -
9 **
10 ** Precession-rate part of the IAU 2000 precession-nutation models
11 ** (part of MHB2000).
12 **
13 ** This function is part of the International Astronomical Union's
14 ** SOFA (Standards Of Fundamental Astronomy) software collection.
15 **
16 ** Status: canonical model.
17 **
18 ** Given:
19 ** date1,date2 double TT as a 2-part Julian Date (Note 1)
20 **
21 ** Returned:
22 ** dpsipr,depspr double precession corrections (Notes 2,3)
23 **
24 ** Notes:
25 **
26 ** 1) The TT date date1+date2 is a Julian Date, apportioned in any
27 ** convenient way between the two arguments. For example,
28 ** JD(TT)=2450123.7 could be expressed in any of these ways,
29 ** among others:
30 **
31 ** date1 date2
32 **
33 ** 2450123.7 0.0 (JD method)
34 ** 2451545.0 -1421.3 (J2000 method)
35 ** 2400000.5 50123.2 (MJD method)
36 ** 2450123.5 0.2 (date & time method)
37 **
38 ** The JD method is the most natural and convenient to use in
39 ** cases where the loss of several decimal digits of resolution
40 ** is acceptable. The J2000 method is best matched to the way
41 ** the argument is handled internally and will deliver the
42 ** optimum resolution. The MJD method and the date & time methods
43 ** are both good compromises between resolution and convenience.
44 **
45 ** 2) The precession adjustments are expressed as "nutation
46 ** components", corrections in longitude and obliquity with respect
47 ** to the J2000.0 equinox and ecliptic.
48 **
49 ** 3) Although the precession adjustments are stated to be with respect
50 ** to Lieske et al. (1977), the MHB2000 model does not specify which
51 ** set of Euler angles are to be used and how the adjustments are to
52 ** be applied. The most literal and straightforward procedure is to
53 ** adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and
54 ** to add dpsipr to psi_A and depspr to both omega_A and eps_A.
55 **
56 ** 4) This is an implementation of one aspect of the IAU 2000A nutation
57 ** model, formally adopted by the IAU General Assembly in 2000,
58 ** namely MHB2000 (Mathews et al. 2002).
59 **
60 ** References:
61 **
62 ** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions
63 ** for the precession quantities based upon the IAU (1976) System of
64 ** Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)
65 **
66 ** Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
67 ** and precession New nutation series for nonrigid Earth and
68 ** insights into the Earth's interior", J.Geophys.Res., 107, B4,
69 ** 2002. The MHB2000 code itself was obtained on 9th September 2002
70 ** from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
71 **
72 ** Wallace, P.T., "Software for Implementing the IAU 2000
73 ** Resolutions", in IERS Workshop 5.1 (2002).
74 **
75 ** This revision: 2021 May 11
76 **
77 ** SOFA release 2021-05-12
78 **
79 ** Copyright (C) 2021 IAU SOFA Board. See notes at end.
80 */
81 {
82 double t;
83
84 /* Precession and obliquity corrections (radians per century) */
85 static const double PRECOR = -0.29965 * DAS2R,
86 OBLCOR = -0.02524 * DAS2R;
87
88
89 /* Interval between fundamental epoch J2000.0 and given date (JC). */
90 t = ((date1 - DJ00) + date2) / DJC;
91
92 /* Precession rate contributions with respect to IAU 1976/80. */
93 *dpsipr = PRECOR * t;
94 *depspr = OBLCOR * t;
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