source: trunk/FACT++/erfa/src/aticq.c@ 18403

Last change on this file since 18403 was 18348, checked in by tbretz, 9 years ago
File size: 7.1 KB
Line 
1#include "erfa.h"
2
3void eraAticq(double ri, double di, eraASTROM *astrom,
4 double *rc, double *dc)
5/*
6** - - - - - - - - -
7** e r a A t i c q
8** - - - - - - - - -
9**
10** Quick CIRS RA,Dec to ICRS astrometric place, given the star-
11** independent astrometry parameters.
12**
13** Use of this function is appropriate when efficiency is important and
14** where many star positions are all to be transformed for one date.
15** The star-independent astrometry parameters can be obtained by
16** calling one of the functions eraApci[13], eraApcg[13], eraApco[13]
17** or eraApcs[13].
18**
19** Given:
20** ri,di double CIRS RA,Dec (radians)
21** astrom eraASTROM* star-independent astrometry parameters:
22** pmt double PM time interval (SSB, Julian years)
23** eb double[3] SSB to observer (vector, au)
24** eh double[3] Sun to observer (unit vector)
25** em double distance from Sun to observer (au)
26** v double[3] barycentric observer velocity (vector, c)
27** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
28** bpn double[3][3] bias-precession-nutation matrix
29** along double longitude + s' (radians)
30** xpl double polar motion xp wrt local meridian (radians)
31** ypl double polar motion yp wrt local meridian (radians)
32** sphi double sine of geodetic latitude
33** cphi double cosine of geodetic latitude
34** diurab double magnitude of diurnal aberration vector
35** eral double "local" Earth rotation angle (radians)
36** refa double refraction constant A (radians)
37** refb double refraction constant B (radians)
38**
39** Returned:
40** rc,dc double ICRS astrometric RA,Dec (radians)
41**
42** Notes:
43**
44** 1) Only the Sun is taken into account in the light deflection
45** correction.
46**
47** 2) Iterative techniques are used for the aberration and light
48** deflection corrections so that the functions eraAtic13 (or
49** eraAticq) and eraAtci13 (or eraAtciq) are accurate inverses;
50** even at the edge of the Sun's disk the discrepancy is only about
51** 1 nanoarcsecond.
52**
53** Called:
54** eraS2c spherical coordinates to unit vector
55** eraTrxp product of transpose of r-matrix and p-vector
56** eraZp zero p-vector
57** eraAb stellar aberration
58** eraLdsun light deflection by the Sun
59** eraC2s p-vector to spherical
60** eraAnp normalize angle into range +/- pi
61**
62** Copyright (C) 2013-2015, NumFOCUS Foundation.
63** Derived, with permission, from the SOFA library. See notes at end of file.
64*/
65{
66 int j, i;
67 double pi[3], ppr[3], pnat[3], pco[3], w, d[3], before[3], r2, r,
68 after[3];
69
70/* CIRS RA,Dec to Cartesian. */
71 eraS2c(ri, di, pi);
72
73/* Bias-precession-nutation, giving GCRS proper direction. */
74 eraTrxp(astrom->bpn, pi, ppr);
75
76/* Aberration, giving GCRS natural direction. */
77 eraZp(d);
78 for (j = 0; j < 2; j++) {
79 r2 = 0.0;
80 for (i = 0; i < 3; i++) {
81 w = ppr[i] - d[i];
82 before[i] = w;
83 r2 += w*w;
84 }
85 r = sqrt(r2);
86 for (i = 0; i < 3; i++) {
87 before[i] /= r;
88 }
89 eraAb(before, astrom->v, astrom->em, astrom->bm1, after);
90 r2 = 0.0;
91 for (i = 0; i < 3; i++) {
92 d[i] = after[i] - before[i];
93 w = ppr[i] - d[i];
94 pnat[i] = w;
95 r2 += w*w;
96 }
97 r = sqrt(r2);
98 for (i = 0; i < 3; i++) {
99 pnat[i] /= r;
100 }
101 }
102
103/* Light deflection by the Sun, giving BCRS coordinate direction. */
104 eraZp(d);
105 for (j = 0; j < 5; j++) {
106 r2 = 0.0;
107 for (i = 0; i < 3; i++) {
108 w = pnat[i] - d[i];
109 before[i] = w;
110 r2 += w*w;
111 }
112 r = sqrt(r2);
113 for (i = 0; i < 3; i++) {
114 before[i] /= r;
115 }
116 eraLdsun(before, astrom->eh, astrom->em, after);
117 r2 = 0.0;
118 for (i = 0; i < 3; i++) {
119 d[i] = after[i] - before[i];
120 w = pnat[i] - d[i];
121 pco[i] = w;
122 r2 += w*w;
123 }
124 r = sqrt(r2);
125 for (i = 0; i < 3; i++) {
126 pco[i] /= r;
127 }
128 }
129
130/* ICRS astrometric RA,Dec. */
131 eraC2s(pco, &w, dc);
132 *rc = eraAnp(w);
133
134/* Finished. */
135
136}
137/*----------------------------------------------------------------------
138**
139**
140** Copyright (C) 2013-2015, NumFOCUS Foundation.
141** All rights reserved.
142**
143** This library is derived, with permission, from the International
144** Astronomical Union's "Standards of Fundamental Astronomy" library,
145** available from http://www.iausofa.org.
146**
147** The ERFA version is intended to retain identical functionality to
148** the SOFA library, but made distinct through different function and
149** file names, as set out in the SOFA license conditions. The SOFA
150** original has a role as a reference standard for the IAU and IERS,
151** and consequently redistribution is permitted only in its unaltered
152** state. The ERFA version is not subject to this restriction and
153** therefore can be included in distributions which do not support the
154** concept of "read only" software.
155**
156** Although the intent is to replicate the SOFA API (other than
157** replacement of prefix names) and results (with the exception of
158** bugs; any that are discovered will be fixed), SOFA is not
159** responsible for any errors found in this version of the library.
160**
161** If you wish to acknowledge the SOFA heritage, please acknowledge
162** that you are using a library derived from SOFA, rather than SOFA
163** itself.
164**
165**
166** TERMS AND CONDITIONS
167**
168** Redistribution and use in source and binary forms, with or without
169** modification, are permitted provided that the following conditions
170** are met:
171**
172** 1 Redistributions of source code must retain the above copyright
173** notice, this list of conditions and the following disclaimer.
174**
175** 2 Redistributions in binary form must reproduce the above copyright
176** notice, this list of conditions and the following disclaimer in
177** the documentation and/or other materials provided with the
178** distribution.
179**
180** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
181** the International Astronomical Union nor the names of its
182** contributors may be used to endorse or promote products derived
183** from this software without specific prior written permission.
184**
185** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
186** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
187** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
188** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
189** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
190** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
191** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
192** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
193** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
194** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
195** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
196** POSSIBILITY OF SUCH DAMAGE.
197**
198*/
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