FACT++  1.0
pr00.c
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1 #include "erfa.h"
2 
3 void eraPr00(double date1, double date2, double *dpsipr, double *depspr)
4 /*
5 ** - - - - - - - -
6 ** e r a P r 0 0
7 ** - - - - - - - -
8 **
9 ** Precession-rate part of the IAU 2000 precession-nutation models
10 ** (part of MHB2000).
11 **
12 ** Given:
13 ** date1,date2 double TT as a 2-part Julian Date (Note 1)
14 **
15 ** Returned:
16 ** dpsipr,depspr double precession corrections (Notes 2,3)
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 precession adjustments are expressed as "nutation
40 ** components", corrections in longitude and obliquity with respect
41 ** to the J2000.0 equinox and ecliptic.
42 **
43 ** 3) Although the precession adjustments are stated to be with respect
44 ** to Lieske et al. (1977), the MHB2000 model does not specify which
45 ** set of Euler angles are to be used and how the adjustments are to
46 ** be applied. The most literal and straightforward procedure is to
47 ** adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and
48 ** to add dpsipr to psi_A and depspr to both omega_A and eps_A.
49 **
50 ** 4) This is an implementation of one aspect of the IAU 2000A nutation
51 ** model, formally adopted by the IAU General Assembly in 2000,
52 ** namely MHB2000 (Mathews et al. 2002).
53 **
54 ** References:
55 **
56 ** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions
57 ** for the precession quantities based upon the IAU (1976) System of
58 ** Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)
59 **
60 ** Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
61 ** and precession New nutation series for nonrigid Earth and
62 ** insights into the Earth's interior", J.Geophys.Res., 107, B4,
63 ** 2002. The MHB2000 code itself was obtained on 9th September 2002
64 ** from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
65 **
66 ** Wallace, P.T., "Software for Implementing the IAU 2000
67 ** Resolutions", in IERS Workshop 5.1 (2002).
68 **
69 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
70 ** Derived, with permission, from the SOFA library. See notes at end of file.
71 */
72 {
73  double t;
74 
75 /* Precession and obliquity corrections (radians per century) */
76  static const double PRECOR = -0.29965 * ERFA_DAS2R,
77  OBLCOR = -0.02524 * ERFA_DAS2R;
78 
79 /* Interval between fundamental epoch J2000.0 and given date (JC). */
80  t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC;
81 
82 /* Precession rate contributions with respect to IAU 1976/80. */
83  *dpsipr = PRECOR * t;
84  *depspr = OBLCOR * t;
85 
86  return;
87 
88 }
89 /*----------------------------------------------------------------------
90 **
91 **
92 ** Copyright (C) 2013-2015, 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 */
ERFA_DJ00
#define ERFA_DJ00
Definition: erfam.h:87
ERFA_DAS2R
#define ERFA_DAS2R
Definition: erfam.h:60
ERFA_DJC
#define ERFA_DJC
Definition: erfam.h:81
t
TT t
Definition: test_client.c:26
eraPr00
void eraPr00(double date1, double date2, double *dpsipr, double *depspr)
Definition: pr00.c:3