1 #include "erfa.h"
2
eraNum06a(double date1,double date2,double rmatn[3][3])3 void eraNum06a(double date1, double date2, double rmatn[3][3])
4 /*
5 ** - - - - - - - - - -
6 ** e r a N u m 0 6 a
7 ** - - - - - - - - - -
8 **
9 ** Form the matrix of nutation for a given date, IAU 2006/2000A model.
10 **
11 ** Given:
12 ** date1,date2 double TT as a 2-part Julian Date (Note 1)
13 **
14 ** Returned:
15 ** rmatn double[3][3] nutation matrix
16 **
17 ** Notes:
18 **
19 ** 1) The TT date date1+date2 is a Julian Date, apportioned in any
20 ** convenient way between the two arguments. For example,
21 ** JD(TT)=2450123.7 could be expressed in any of these ways,
22 ** among others:
23 **
24 ** date1 date2
25 **
26 ** 2450123.7 0.0 (JD method)
27 ** 2451545.0 -1421.3 (J2000 method)
28 ** 2400000.5 50123.2 (MJD method)
29 ** 2450123.5 0.2 (date & time method)
30 **
31 ** The JD method is the most natural and convenient to use in
32 ** cases where the loss of several decimal digits of resolution
33 ** is acceptable. The J2000 method is best matched to the way
34 ** the argument is handled internally and will deliver the
35 ** optimum resolution. The MJD method and the date & time methods
36 ** are both good compromises between resolution and convenience.
37 **
38 ** 2) The matrix operates in the sense V(true) = rmatn * V(mean), where
39 ** the p-vector V(true) is with respect to the true equatorial triad
40 ** of date and the p-vector V(mean) is with respect to the mean
41 ** equatorial triad of date.
42 **
43 ** Called:
44 ** eraObl06 mean obliquity, IAU 2006
45 ** eraNut06a nutation, IAU 2006/2000A
46 ** eraNumat form nutation matrix
47 **
48 ** Reference:
49 **
50 ** Explanatory Supplement to the Astronomical Almanac,
51 ** P. Kenneth Seidelmann (ed), University Science Books (1992),
52 ** Section 3.222-3 (p114).
53 **
54 ** This revision: 2021 May 11
55 **
56 ** Copyright (C) 2013-2021, NumFOCUS Foundation.
57 ** Derived, with permission, from the SOFA library. See notes at end of file.
58 */
59 {
60 double eps, dp, de;
61
62
63 /* Mean obliquity. */
64 eps = eraObl06(date1, date2);
65
66 /* Nutation components. */
67 eraNut06a(date1, date2, &dp, &de);
68
69 /* Nutation matrix. */
70 eraNumat(eps, dp, de, rmatn);
71
72 /* Finished. */
73
74 }
75 /*----------------------------------------------------------------------
76 **
77 **
78 ** Copyright (C) 2013-2021, NumFOCUS Foundation.
79 ** All rights reserved.
80 **
81 ** This library is derived, with permission, from the International
82 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
83 ** available from http://www.iausofa.org.
84 **
85 ** The ERFA version is intended to retain identical functionality to
86 ** the SOFA library, but made distinct through different function and
87 ** file names, as set out in the SOFA license conditions. The SOFA
88 ** original has a role as a reference standard for the IAU and IERS,
89 ** and consequently redistribution is permitted only in its unaltered
90 ** state. The ERFA version is not subject to this restriction and
91 ** therefore can be included in distributions which do not support the
92 ** concept of "read only" software.
93 **
94 ** Although the intent is to replicate the SOFA API (other than
95 ** replacement of prefix names) and results (with the exception of
96 ** bugs; any that are discovered will be fixed), SOFA is not
97 ** responsible for any errors found in this version of the library.
98 **
99 ** If you wish to acknowledge the SOFA heritage, please acknowledge
100 ** that you are using a library derived from SOFA, rather than SOFA
101 ** itself.
102 **
103 **
104 ** TERMS AND CONDITIONS
105 **
106 ** Redistribution and use in source and binary forms, with or without
107 ** modification, are permitted provided that the following conditions
108 ** are met:
109 **
110 ** 1 Redistributions of source code must retain the above copyright
111 ** notice, this list of conditions and the following disclaimer.
112 **
113 ** 2 Redistributions in binary form must reproduce the above copyright
114 ** notice, this list of conditions and the following disclaimer in
115 ** the documentation and/or other materials provided with the
116 ** distribution.
117 **
118 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
119 ** the International Astronomical Union nor the names of its
120 ** contributors may be used to endorse or promote products derived
121 ** from this software without specific prior written permission.
122 **
123 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
124 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
125 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
126 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
127 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
128 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
129 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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135 **
136 */
137