source: trunk/FACT++/erfa/src/hfk5z.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 eraHfk5z(double rh, double dh, double date1, double date2,
4 double *r5, double *d5, double *dr5, double *dd5)
5/*
6** - - - - - - - - -
7** e r a H f k 5 z
8** - - - - - - - - -
9**
10** Transform a Hipparcos star position into FK5 J2000.0, assuming
11** zero Hipparcos proper motion.
12**
13** Given:
14** rh double Hipparcos RA (radians)
15** dh double Hipparcos Dec (radians)
16** date1,date2 double TDB date (Note 1)
17**
18** Returned (all FK5, equinox J2000.0, date date1+date2):
19** r5 double RA (radians)
20** d5 double Dec (radians)
21** dr5 double FK5 RA proper motion (rad/year, Note 4)
22** dd5 double Dec proper motion (rad/year, Note 4)
23**
24** Notes:
25**
26** 1) The TT date date1+date2 is a Julian Date, apportioned in any
27** convenient way between the two arguments. For example,
28** JD(TT)=2450123.7 could be expressed in any of these ways,
29** among others:
30**
31** date1 date2
32**
33** 2450123.7 0.0 (JD method)
34** 2451545.0 -1421.3 (J2000 method)
35** 2400000.5 50123.2 (MJD method)
36** 2450123.5 0.2 (date & time method)
37**
38** The JD method is the most natural and convenient to use in
39** cases where the loss of several decimal digits of resolution
40** is acceptable. The J2000 method is best matched to the way
41** the argument is handled internally and will deliver the
42** optimum resolution. The MJD method and the date & time methods
43** are both good compromises between resolution and convenience.
44**
45** 2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
46**
47** 3) The FK5 to Hipparcos transformation is modeled as a pure rotation
48** and spin; zonal errors in the FK5 catalogue are not taken into
49** account.
50**
51** 4) It was the intention that Hipparcos should be a close
52** approximation to an inertial frame, so that distant objects have
53** zero proper motion; such objects have (in general) non-zero
54** proper motion in FK5, and this function returns those fictitious
55** proper motions.
56**
57** 5) The position returned by this function is in the FK5 J2000.0
58** reference system but at date date1+date2.
59**
60** 6) See also eraFk52h, eraH2fk5, eraFk5zhz.
61**
62** Called:
63** eraS2c spherical coordinates to unit vector
64** eraFk5hip FK5 to Hipparcos rotation and spin
65** eraRxp product of r-matrix and p-vector
66** eraSxp multiply p-vector by scalar
67** eraRxr product of two r-matrices
68** eraTrxp product of transpose of r-matrix and p-vector
69** eraPxp vector product of two p-vectors
70** eraPv2s pv-vector to spherical
71** eraAnp normalize angle into range 0 to 2pi
72**
73** Reference:
74**
75** F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739.
76**
77** Copyright (C) 2013-2015, NumFOCUS Foundation.
78** Derived, with permission, from the SOFA library. See notes at end of file.
79*/
80{
81 double t, ph[3], r5h[3][3], s5h[3], sh[3], vst[3],
82 rst[3][3], r5ht[3][3], pv5e[2][3], vv[3],
83 w, r, v;
84
85/* Time interval from fundamental epoch J2000.0 to given date (JY). */
86 t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJY;
87
88/* Hipparcos barycentric position vector (normalized). */
89 eraS2c(rh, dh, ph);
90
91/* FK5 to Hipparcos orientation matrix and spin vector. */
92 eraFk5hip(r5h, s5h);
93
94/* Rotate the spin into the Hipparcos system. */
95 eraRxp(r5h, s5h, sh);
96
97/* Accumulated Hipparcos wrt FK5 spin over that interval. */
98 eraSxp(t, s5h, vst);
99
100/* Express the accumulated spin as a rotation matrix. */
101 eraRv2m(vst, rst);
102
103/* Rotation matrix: accumulated spin, then FK5 to Hipparcos. */
104 eraRxr(r5h, rst, r5ht);
105
106/* De-orient & de-spin the Hipparcos position into FK5 J2000.0. */
107 eraTrxp(r5ht, ph, pv5e[0]);
108
109/* Apply spin to the position giving a space motion. */
110 eraPxp(sh, ph, vv);
111
112/* De-orient & de-spin the Hipparcos space motion into FK5 J2000.0. */
113 eraTrxp(r5ht, vv, pv5e[1]);
114
115/* FK5 position/velocity pv-vector to spherical. */
116 eraPv2s(pv5e, &w, d5, &r, dr5, dd5, &v);
117 *r5 = eraAnp(w);
118
119 return;
120
121}
122/*----------------------------------------------------------------------
123**
124**
125** Copyright (C) 2013-2015, NumFOCUS Foundation.
126** All rights reserved.
127**
128** This library is derived, with permission, from the International
129** Astronomical Union's "Standards of Fundamental Astronomy" library,
130** available from http://www.iausofa.org.
131**
132** The ERFA version is intended to retain identical functionality to
133** the SOFA library, but made distinct through different function and
134** file names, as set out in the SOFA license conditions. The SOFA
135** original has a role as a reference standard for the IAU and IERS,
136** and consequently redistribution is permitted only in its unaltered
137** state. The ERFA version is not subject to this restriction and
138** therefore can be included in distributions which do not support the
139** concept of "read only" software.
140**
141** Although the intent is to replicate the SOFA API (other than
142** replacement of prefix names) and results (with the exception of
143** bugs; any that are discovered will be fixed), SOFA is not
144** responsible for any errors found in this version of the library.
145**
146** If you wish to acknowledge the SOFA heritage, please acknowledge
147** that you are using a library derived from SOFA, rather than SOFA
148** itself.
149**
150**
151** TERMS AND CONDITIONS
152**
153** Redistribution and use in source and binary forms, with or without
154** modification, are permitted provided that the following conditions
155** are met:
156**
157** 1 Redistributions of source code must retain the above copyright
158** notice, this list of conditions and the following disclaimer.
159**
160** 2 Redistributions in binary form must reproduce the above copyright
161** notice, this list of conditions and the following disclaimer in
162** the documentation and/or other materials provided with the
163** distribution.
164**
165** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
166** the International Astronomical Union nor the names of its
167** contributors may be used to endorse or promote products derived
168** from this software without specific prior written permission.
169**
170** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
171** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
172** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
173** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
174** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
175** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
176** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
177** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
178** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
179** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
180** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
181** POSSIBILITY OF SUCH DAMAGE.
182**
183*/
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