source: trunk/FACT++/erfa/src/apcg13.c@ 18348

Last change on this file since 18348 was 18348, checked in by tbretz, 9 years ago
File size: 7.6 KB
Line 
1#include "erfa.h"
2
3void eraApcg13(double date1, double date2, eraASTROM *astrom)
4/*
5** - - - - - - - - - -
6** e r a A p c g 1 3
7** - - - - - - - - - -
8**
9** For a geocentric observer, prepare star-independent astrometry
10** parameters for transformations between ICRS and GCRS coordinates.
11** The caller supplies the date, and ERFA models are used to predict
12** the Earth ephemeris.
13**
14** The parameters produced by this function are required in the
15** parallax, light deflection and aberration parts of the astrometric
16** transformation chain.
17**
18** Given:
19** date1 double TDB as a 2-part...
20** date2 double ...Julian Date (Note 1)
21**
22** Returned:
23** astrom eraASTROM* star-independent astrometry parameters:
24** pmt double PM time interval (SSB, Julian years)
25** eb double[3] SSB to observer (vector, au)
26** eh double[3] Sun to observer (unit vector)
27** em double distance from Sun to observer (au)
28** v double[3] barycentric observer velocity (vector, c)
29** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
30** bpn double[3][3] bias-precession-nutation matrix
31** along double unchanged
32** xpl double unchanged
33** ypl double unchanged
34** sphi double unchanged
35** cphi double unchanged
36** diurab double unchanged
37** eral double unchanged
38** refa double unchanged
39** refb double unchanged
40**
41** Notes:
42**
43** 1) The TDB date date1+date2 is a Julian Date, apportioned in any
44** convenient way between the two arguments. For example,
45** JD(TDB)=2450123.7 could be expressed in any of these ways, among
46** others:
47**
48** date1 date2
49**
50** 2450123.7 0.0 (JD method)
51** 2451545.0 -1421.3 (J2000 method)
52** 2400000.5 50123.2 (MJD method)
53** 2450123.5 0.2 (date & time method)
54**
55** The JD method is the most natural and convenient to use in cases
56** where the loss of several decimal digits of resolution is
57** acceptable. The J2000 method is best matched to the way the
58** argument is handled internally and will deliver the optimum
59** resolution. The MJD method and the date & time methods are both
60** good compromises between resolution and convenience. For most
61** applications of this function the choice will not be at all
62** critical.
63**
64** TT can be used instead of TDB without any significant impact on
65** accuracy.
66**
67** 2) All the vectors are with respect to BCRS axes.
68**
69** 3) In cases where the caller wishes to supply his own Earth
70** ephemeris, the function eraApcg can be used instead of the present
71** function.
72**
73** 4) This is one of several functions that inserts into the astrom
74** structure star-independent parameters needed for the chain of
75** astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
76**
77** The various functions support different classes of observer and
78** portions of the transformation chain:
79**
80** functions observer transformation
81**
82** eraApcg eraApcg13 geocentric ICRS <-> GCRS
83** eraApci eraApci13 terrestrial ICRS <-> CIRS
84** eraApco eraApco13 terrestrial ICRS <-> observed
85** eraApcs eraApcs13 space ICRS <-> GCRS
86** eraAper eraAper13 terrestrial update Earth rotation
87** eraApio eraApio13 terrestrial CIRS <-> observed
88**
89** Those with names ending in "13" use contemporary ERFA models to
90** compute the various ephemerides. The others accept ephemerides
91** supplied by the caller.
92**
93** The transformation from ICRS to GCRS covers space motion,
94** parallax, light deflection, and aberration. From GCRS to CIRS
95** comprises frame bias and precession-nutation. From CIRS to
96** observed takes account of Earth rotation, polar motion, diurnal
97** aberration and parallax (unless subsumed into the ICRS <-> GCRS
98** transformation), and atmospheric refraction.
99**
100** 5) The context structure astrom produced by this function is used by
101** eraAtciq* and eraAticq*.
102**
103** Called:
104** eraEpv00 Earth position and velocity
105** eraApcg astrometry parameters, ICRS-GCRS, geocenter
106**
107** Copyright (C) 2013-2015, NumFOCUS Foundation.
108** Derived, with permission, from the SOFA library. See notes at end of file.
109*/
110{
111 double ehpv[2][3], ebpv[2][3];
112
113/* Earth barycentric & heliocentric position/velocity (au, au/d). */
114 (void) eraEpv00(date1, date2, ehpv, ebpv);
115
116/* Compute the star-independent astrometry parameters. */
117 eraApcg(date1, date2, ebpv, ehpv[0], astrom);
118
119/* Finished. */
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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