1 /*
2 * - - - - - - - - -
3 * g a l _ p n 0 0
4 * - - - - - - - - -
5 *
6 * This routine is part of the General Astrodynamics Library
7 *
8 * Description:
9 *
10 * Precession-nutation, IAU 2000 model: a multi-purpose routine,
11 * supporting classical (equinox-based) use directly and CIO-based
12 * use indirectly.
13 *
14 * This routine is an independent translation of a FORTRAN routine
15 * that is part of IAU's SOFA software collection.
16 *
17 * Status:
18 *
19 * support routine.
20 *
21 * Given:
22 *
23 * date1,date2 d TT as a 2-part Julian Date (Note 1)
24 * dpsi,deps d nutation (Note 2)
25 *
26 * Returned:
27 *
28 * *epsa d mean obliquity (Note 3)
29 * rb d[3][3] frame bias matrix (Note 4)
30 * rp d[3][3] precession matrix (Note 5)
31 * rbp d[3][3] bias-precession matrix (Note 6)
32 * rn d[3][3] nutation matrix (Note 7)
33 * rbpn d[3][3] GCRS-to-true matrix (Note 8)
34 *
35 * Notes:
36 *
37 * 1) The TT date date1+date2 is a Julian Date, apportioned in any
38 * convenient way between the two arguments. For example,
39 * JD(TT)=2450123.7 could be expressed in any of these ways,
40 * among others:
41 *
42 * date1 date2
43 *
44 * 2450123.7 0.0 (JD method)
45 * 2451545.0 -1421.3 (J2000 method)
46 * 2400000.5 50123.2 (MJD method)
47 * 2450123.5 0.2 (date & time method)
48 *
49 * The JD method is the most natural and convenient to use in
50 * cases where the loss of several decimal digits of resolution
51 * is acceptable. The J2000 method is best matched to the way
52 * the argument is handled internally and will deliver the
53 * optimum resolution. The MJD method and the date & time methods
54 * are both good compromises between resolution and convenience.
55 *
56 * 2) The caller is responsible for providing the nutation components;
57 * they are in longitude and obliquity, in radians and are with
58 * respect to the equinox and ecliptic of date. For high-accuracy
59 * applications, free core nutation should be included as well as
60 * any other relevant corrections to the position of the CIP.
61 *
62 * 3) The returned mean obliquity is consistent with the IAU 2000
63 * precession-nutation models.
64 *
65 * 4) The matrix rb transforms vectors from GCRS to J2000 mean equator
66 * and equinox by applying frame bias.
67 *
68 * 5) The matrix rp transforms vectors from J2000 mean equator and
69 * equinox to mean equator and equinox of date by applying
70 * precession.
71 *
72 * 6) The matrix rbp transforms vectors from GCRS to mean equator and
73 * equinox of date by applying frame bias then precession. It is the
74 * product rp x rb.
75 *
76 * 7) The matrix rn transforms vectors from mean equator and equinox of
77 * date to true equator and equinox of date by applying the nutation
78 * (luni-solar + planetary).
79 *
80 * 8) The matrix rbpn transforms vectors from GCRS to true equator and
81 * equinox of date. It is the product rn x rbp, applying frame bias,
82 * precession and nutation in that order.
83 *
84 * Called:
85 *
86 * gal_pr00 IAU 2000 precession adjustments
87 * gal_obl80 mean obliquity, IAU 1980
88 * gal_bp00 frame bias and precession matrices, IAU 2000
89 * gal_numat form nutation matrix
90 * gal_rxr product of two r-matrices
91 *
92 * References:
93 *
94 * Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
95 * "Expressions for the Celestial Intermediate Pole and Celestial
96 * Ephemeris Origin consistent with the IAU 2000A precession-nutation
97 * model", Astronomy & Astrophysics, 400, 1145-1154 (2003)
98 *
99 * n.b. The celestial ephemeris origin (CEO) was renamed "celestial
100 * intermediate origin" (CIO) by IAU 2006 Resolution 2.
101 *
102 * This revision:
103 *
104 * 2007 April 11 ( c version 2008 February 4 )
105 *
106 *
107 * Copyright (C) 2008 Paul C. L. Willmott. See notes at end.
108 *
109 *-----------------------------------------------------------------------
110 */
111
112 #include "gal_pn00.h"
113 #include "gal_pr00.h"
114 #include "gal_obl80.h"
115 #include "gal_bp00.h"
116 #include "gal_numat.h"
117 #include "gal_rxr.h"
118
119 void
gal_pn00(double date1,double date2,double dpsi,double deps,double * epsa,double rb[3][3],double rp[3][3],double rbp[3][3],double rn[3][3],double rbpn[3][3])120 gal_pn00
121 (
122 double date1,
123 double date2,
124 double dpsi,
125 double deps,
126 double *epsa,
127 double rb[3][3],
128 double rp[3][3],
129 double rbp[3][3],
130 double rn[3][3],
131 double rbpn[3][3]
132 )
133 {
134
135 double dpsipr, depspr ;
136
137 /*
138 * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
139 */
140
141 /*
142 * IAU 2000 precession-rate adjustments.
143 */
144
145 gal_pr00 ( date1, date2, &dpsipr, &depspr ) ;
146
147 /*
148 * Mean obliquity, consistent with IAU 2000 precession-nutation.
149 */
150
151 *epsa = gal_obl80 ( date1, date2 ) + depspr ;
152
153 /*
154 * Frame bias and precession matrices and their product.
155 */
156
157 gal_bp00 ( date1, date2, rb, rp, rbp ) ;
158
159 /*
160 * Nutation matrix.
161 */
162
163 gal_numat ( *epsa, dpsi, deps, rn ) ;
164
165 /*
166 * Bias-precession-nutation matrix (classical).
167 */
168
169 gal_rxr ( rn, rbp, rbpn ) ;
170
171 /*
172 * Finished.
173 */
174
175 }
176
177 /*
178 * gal - General Astrodynamics Library
179 * Copyright (C) 2008 Paul C. L. Willmott
180 *
181 * This program is free software; you can redistribute it and/or modify
182 * it under the terms of the GNU General Public License as published by
183 * the Free Software Foundation; either version 2 of the License, or
184 * (at your option) any later version.
185 *
186 * This program is distributed in the hope that it will be useful,
187 * but WITHOUT ANY WARRANTY; without even the implied warranty of
188 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
189 * GNU General Public License for more details.
190 *
191 * You should have received a copy of the GNU General Public License along
192 * with this program; if not, write to the Free Software Foundation, Inc.,
193 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
194 *
195 * Contact:
196 *
197 * Paul Willmott
198 * vp9mu@amsat.org
199 */
200