source: branches/FACT++_lidctrl_usb/erfa/src/fk5hz.c@ 19875

Last change on this file since 19875 was 18711, checked in by tbretz, 10 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 6.5 KB
Line 
1#include "erfa.h"
2
3void eraFk5hz(double r5, double d5, double date1, double date2,
4 double *rh, double *dh)
5/*
6** - - - - - - - - -
7** e r a F k 5 h z
8** - - - - - - - - -
9**
10** Transform an FK5 (J2000.0) star position into the system of the
11** Hipparcos catalogue, assuming zero Hipparcos proper motion.
12**
13** Given:
14** r5 double FK5 RA (radians), equinox J2000.0, at date
15** d5 double FK5 Dec (radians), equinox J2000.0, at date
16** date1,date2 double TDB date (Notes 1,2)
17**
18** Returned:
19** rh double Hipparcos RA (radians)
20** dh double Hipparcos Dec (radians)
21**
22** Notes:
23**
24** 1) This function converts a star position from the FK5 system to
25** the Hipparcos system, in such a way that the Hipparcos proper
26** motion is zero. Because such a star has, in general, a non-zero
27** proper motion in the FK5 system, the function requires the date
28** at which the position in the FK5 system was determined.
29**
30** 2) The TT date date1+date2 is a Julian Date, apportioned in any
31** convenient way between the two arguments. For example,
32** JD(TT)=2450123.7 could be expressed in any of these ways,
33** among others:
34**
35** date1 date2
36**
37** 2450123.7 0.0 (JD method)
38** 2451545.0 -1421.3 (J2000 method)
39** 2400000.5 50123.2 (MJD method)
40** 2450123.5 0.2 (date & time method)
41**
42** The JD method is the most natural and convenient to use in
43** cases where the loss of several decimal digits of resolution
44** is acceptable. The J2000 method is best matched to the way
45** the argument is handled internally and will deliver the
46** optimum resolution. The MJD method and the date & time methods
47** are both good compromises between resolution and convenience.
48**
49** 3) The FK5 to Hipparcos transformation is modeled as a pure
50** rotation and spin; zonal errors in the FK5 catalogue are not
51** taken into account.
52**
53** 4) The position returned by this function is in the Hipparcos
54** reference system but at date date1+date2.
55**
56** 5) See also eraFk52h, eraH2fk5, eraHfk5z.
57**
58** Called:
59** eraS2c spherical coordinates to unit vector
60** eraFk5hip FK5 to Hipparcos rotation and spin
61** eraSxp multiply p-vector by scalar
62** eraRv2m r-vector to r-matrix
63** eraTrxp product of transpose of r-matrix and p-vector
64** eraPxp vector product of two p-vectors
65** eraC2s p-vector to spherical
66** eraAnp normalize angle into range 0 to 2pi
67**
68** Reference:
69**
70** F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739.
71**
72** Copyright (C) 2013-2016, NumFOCUS Foundation.
73** Derived, with permission, from the SOFA library. See notes at end of file.
74*/
75{
76 double t, p5e[3], r5h[3][3], s5h[3], vst[3], rst[3][3], p5[3],
77 ph[3], w;
78
79
80/* Interval from given date to fundamental epoch J2000.0 (JY). */
81 t = - ((date1 - ERFA_DJ00) + date2) / ERFA_DJY;
82
83/* FK5 barycentric position vector. */
84 eraS2c(r5, d5, p5e);
85
86/* FK5 to Hipparcos orientation matrix and spin vector. */
87 eraFk5hip(r5h, s5h);
88
89/* Accumulated Hipparcos wrt FK5 spin over that interval. */
90 eraSxp(t, s5h, vst);
91
92/* Express the accumulated spin as a rotation matrix. */
93 eraRv2m(vst, rst);
94
95/* Derotate the vector's FK5 axes back to date. */
96 eraTrxp(rst, p5e, p5);
97
98/* Rotate the vector into the Hipparcos system. */
99 eraRxp(r5h, p5, ph);
100
101/* Hipparcos vector to spherical. */
102 eraC2s(ph, &w, dh);
103 *rh = eraAnp(w);
104
105 return;
106
107}
108/*----------------------------------------------------------------------
109**
110**
111** Copyright (C) 2013-2016, NumFOCUS Foundation.
112** All rights reserved.
113**
114** This library is derived, with permission, from the International
115** Astronomical Union's "Standards of Fundamental Astronomy" library,
116** available from http://www.iausofa.org.
117**
118** The ERFA version is intended to retain identical functionality to
119** the SOFA library, but made distinct through different function and
120** file names, as set out in the SOFA license conditions. The SOFA
121** original has a role as a reference standard for the IAU and IERS,
122** and consequently redistribution is permitted only in its unaltered
123** state. The ERFA version is not subject to this restriction and
124** therefore can be included in distributions which do not support the
125** concept of "read only" software.
126**
127** Although the intent is to replicate the SOFA API (other than
128** replacement of prefix names) and results (with the exception of
129** bugs; any that are discovered will be fixed), SOFA is not
130** responsible for any errors found in this version of the library.
131**
132** If you wish to acknowledge the SOFA heritage, please acknowledge
133** that you are using a library derived from SOFA, rather than SOFA
134** itself.
135**
136**
137** TERMS AND CONDITIONS
138**
139** Redistribution and use in source and binary forms, with or without
140** modification, are permitted provided that the following conditions
141** are met:
142**
143** 1 Redistributions of source code must retain the above copyright
144** notice, this list of conditions and the following disclaimer.
145**
146** 2 Redistributions in binary form must reproduce the above copyright
147** notice, this list of conditions and the following disclaimer in
148** the documentation and/or other materials provided with the
149** distribution.
150**
151** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
152** the International Astronomical Union nor the names of its
153** contributors may be used to endorse or promote products derived
154** from this software without specific prior written permission.
155**
156** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
157** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
158** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
159** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
160** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
161** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
162** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
163** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
164** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
165** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
166** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
167** POSSIBILITY OF SUCH DAMAGE.
168**
169*/
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