source: trunk/FACT++/erfa/src/aticqn.c@ 18921

Last change on this file since 18921 was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 8.9 KB
Line 
1#include "erfa.h"
2
3void eraAticqn(double ri, double di, eraASTROM *astrom,
4 int n, eraLDBODY b[], double *rc, double *dc)
5/*
6** - - - - - - - - -
7** e r a A t i c q n
8** - - - - - - - - -
9**
10** Quick CIRS to ICRS astrometric place transformation, given the star-
11** independent astrometry parameters plus a list of light-deflecting
12** bodies.
13**
14** Use of this function is appropriate when efficiency is important and
15** where many star positions are all to be transformed for one date.
16** The star-independent astrometry parameters can be obtained by
17** calling one of the functions eraApci[13], eraApcg[13], eraApco[13]
18** or eraApcs[13].
19*
20* If the only light-deflecting body to be taken into account is the
21* Sun, the eraAticq function can be used instead.
22**
23** Given:
24** ri,di double CIRS RA,Dec (radians)
25** astrom eraASTROM* star-independent astrometry parameters:
26** pmt double PM time interval (SSB, Julian years)
27** eb double[3] SSB to observer (vector, au)
28** eh double[3] Sun to observer (unit vector)
29** em double distance from Sun to observer (au)
30** v double[3] barycentric observer velocity (vector, c)
31** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
32** bpn double[3][3] bias-precession-nutation matrix
33** along double longitude + s' (radians)
34** xpl double polar motion xp wrt local meridian (radians)
35** ypl double polar motion yp wrt local meridian (radians)
36** sphi double sine of geodetic latitude
37** cphi double cosine of geodetic latitude
38** diurab double magnitude of diurnal aberration vector
39** eral double "local" Earth rotation angle (radians)
40** refa double refraction constant A (radians)
41** refb double refraction constant B (radians)
42** n int number of bodies (Note 3)
43** b eraLDBODY[n] data for each of the n bodies (Notes 3,4):
44** bm double mass of the body (solar masses, Note 5)
45** dl double deflection limiter (Note 6)
46** pv [2][3] barycentric PV of the body (au, au/day)
47**
48** Returned:
49** rc,dc double ICRS astrometric RA,Dec (radians)
50**
51** Notes:
52**
53** 1) Iterative techniques are used for the aberration and light
54** deflection corrections so that the functions eraAticqn and
55** eraAtciqn are accurate inverses; even at the edge of the Sun's
56** disk the discrepancy is only about 1 nanoarcsecond.
57**
58** 2) If the only light-deflecting body to be taken into account is the
59** Sun, the eraAticq function can be used instead.
60**
61** 3) The struct b contains n entries, one for each body to be
62** considered. If n = 0, no gravitational light deflection will be
63** applied, not even for the Sun.
64**
65** 4) The struct b should include an entry for the Sun as well as for
66** any planet or other body to be taken into account. The entries
67** should be in the order in which the light passes the body.
68**
69** 5) In the entry in the b struct for body i, the mass parameter
70** b[i].bm can, as required, be adjusted in order to allow for such
71** effects as quadrupole field.
72**
73** 6) The deflection limiter parameter b[i].dl is phi^2/2, where phi is
74** the angular separation (in radians) between star and body at
75** which limiting is applied. As phi shrinks below the chosen
76** threshold, the deflection is artificially reduced, reaching zero
77** for phi = 0. Example values suitable for a terrestrial
78** observer, together with masses, are as follows:
79**
80** body i b[i].bm b[i].dl
81**
82** Sun 1.0 6e-6
83** Jupiter 0.00095435 3e-9
84** Saturn 0.00028574 3e-10
85**
86** 7) For efficiency, validation of the contents of the b array is
87** omitted. The supplied masses must be greater than zero, the
88** position and velocity vectors must be right, and the deflection
89** limiter greater than zero.
90**
91** Called:
92** eraS2c spherical coordinates to unit vector
93** eraTrxp product of transpose of r-matrix and p-vector
94** eraZp zero p-vector
95** eraAb stellar aberration
96** eraLdn light deflection by n bodies
97** eraC2s p-vector to spherical
98** eraAnp normalize angle into range +/- pi
99**
100** Copyright (C) 2013-2017, NumFOCUS Foundation.
101** Derived, with permission, from the SOFA library. See notes at end of file.
102*/
103{
104 int j, i;
105 double pi[3], ppr[3], pnat[3], pco[3], w, d[3], before[3], r2, r,
106 after[3];
107
108
109/* CIRS RA,Dec to Cartesian. */
110 eraS2c(ri, di, pi);
111
112/* Bias-precession-nutation, giving GCRS proper direction. */
113 eraTrxp(astrom->bpn, pi, ppr);
114
115/* Aberration, giving GCRS natural direction. */
116 eraZp(d);
117 for (j = 0; j < 2; j++) {
118 r2 = 0.0;
119 for (i = 0; i < 3; i++) {
120 w = ppr[i] - d[i];
121 before[i] = w;
122 r2 += w*w;
123 }
124 r = sqrt(r2);
125 for (i = 0; i < 3; i++) {
126 before[i] /= r;
127 }
128 eraAb(before, astrom->v, astrom->em, astrom->bm1, after);
129 r2 = 0.0;
130 for (i = 0; i < 3; i++) {
131 d[i] = after[i] - before[i];
132 w = ppr[i] - d[i];
133 pnat[i] = w;
134 r2 += w*w;
135 }
136 r = sqrt(r2);
137 for (i = 0; i < 3; i++) {
138 pnat[i] /= r;
139 }
140 }
141
142/* Light deflection, giving BCRS coordinate direction. */
143 eraZp(d);
144 for (j = 0; j < 5; j++) {
145 r2 = 0.0;
146 for (i = 0; i < 3; i++) {
147 w = pnat[i] - d[i];
148 before[i] = w;
149 r2 += w*w;
150 }
151 r = sqrt(r2);
152 for (i = 0; i < 3; i++) {
153 before[i] /= r;
154 }
155 eraLdn(n, b, astrom->eb, before, after);
156 r2 = 0.0;
157 for (i = 0; i < 3; i++) {
158 d[i] = after[i] - before[i];
159 w = pnat[i] - d[i];
160 pco[i] = w;
161 r2 += w*w;
162 }
163 r = sqrt(r2);
164 for (i = 0; i < 3; i++) {
165 pco[i] /= r;
166 }
167 }
168
169/* ICRS astrometric RA,Dec. */
170 eraC2s(pco, &w, dc);
171 *rc = eraAnp(w);
172
173/* Finished. */
174
175}
176/*----------------------------------------------------------------------
177**
178**
179** Copyright (C) 2013-2017, NumFOCUS Foundation.
180** All rights reserved.
181**
182** This library is derived, with permission, from the International
183** Astronomical Union's "Standards of Fundamental Astronomy" library,
184** available from http://www.iausofa.org.
185**
186** The ERFA version is intended to retain identical functionality to
187** the SOFA library, but made distinct through different function and
188** file names, as set out in the SOFA license conditions. The SOFA
189** original has a role as a reference standard for the IAU and IERS,
190** and consequently redistribution is permitted only in its unaltered
191** state. The ERFA version is not subject to this restriction and
192** therefore can be included in distributions which do not support the
193** concept of "read only" software.
194**
195** Although the intent is to replicate the SOFA API (other than
196** replacement of prefix names) and results (with the exception of
197** bugs; any that are discovered will be fixed), SOFA is not
198** responsible for any errors found in this version of the library.
199**
200** If you wish to acknowledge the SOFA heritage, please acknowledge
201** that you are using a library derived from SOFA, rather than SOFA
202** itself.
203**
204**
205** TERMS AND CONDITIONS
206**
207** Redistribution and use in source and binary forms, with or without
208** modification, are permitted provided that the following conditions
209** are met:
210**
211** 1 Redistributions of source code must retain the above copyright
212** notice, this list of conditions and the following disclaimer.
213**
214** 2 Redistributions in binary form must reproduce the above copyright
215** notice, this list of conditions and the following disclaimer in
216** the documentation and/or other materials provided with the
217** distribution.
218**
219** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
220** the International Astronomical Union nor the names of its
221** contributors may be used to endorse or promote products derived
222** from this software without specific prior written permission.
223**
224** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
225** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
226** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
227** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
228** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
229** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
230** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
231** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
232** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
233** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
234** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
235** POSSIBILITY OF SUCH DAMAGE.
236**
237*/
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