FACT++  1.0
apcg.c
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1 #include "erfa.h"
2 
3 void eraApcg(double date1, double date2,
4  double ebpv[2][3], double ehp[3],
5  eraASTROM *astrom)
6 /*
7 ** - - - - - - - -
8 ** e r a A p c g
9 ** - - - - - - - -
10 **
11 ** For a geocentric observer, prepare star-independent astrometry
12 ** parameters for transformations between ICRS and GCRS coordinates.
13 ** The Earth ephemeris is supplied by the caller.
14 **
15 ** The parameters produced by this function are required in the
16 ** parallax, light deflection and aberration parts of the astrometric
17 ** transformation chain.
18 **
19 ** Given:
20 ** date1 double TDB as a 2-part...
21 ** date2 double ...Julian Date (Note 1)
22 ** ebpv double[2][3] Earth barycentric pos/vel (au, au/day)
23 ** ehp double[3] Earth heliocentric position (au)
24 **
25 ** Returned:
26 ** astrom eraASTROM* star-independent astrometry parameters:
27 ** pmt double PM time interval (SSB, Julian years)
28 ** eb double[3] SSB to observer (vector, au)
29 ** eh double[3] Sun to observer (unit vector)
30 ** em double distance from Sun to observer (au)
31 ** v double[3] barycentric observer velocity (vector, c)
32 ** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
33 ** bpn double[3][3] bias-precession-nutation matrix
34 ** along double unchanged
35 ** xpl double unchanged
36 ** ypl double unchanged
37 ** sphi double unchanged
38 ** cphi double unchanged
39 ** diurab double unchanged
40 ** eral double unchanged
41 ** refa double unchanged
42 ** refb double unchanged
43 **
44 ** Notes:
45 **
46 ** 1) The TDB date date1+date2 is a Julian Date, apportioned in any
47 ** convenient way between the two arguments. For example,
48 ** JD(TDB)=2450123.7 could be expressed in any of these ways, among
49 ** others:
50 **
51 ** date1 date2
52 **
53 ** 2450123.7 0.0 (JD method)
54 ** 2451545.0 -1421.3 (J2000 method)
55 ** 2400000.5 50123.2 (MJD method)
56 ** 2450123.5 0.2 (date & time method)
57 **
58 ** The JD method is the most natural and convenient to use in cases
59 ** where the loss of several decimal digits of resolution is
60 ** acceptable. The J2000 method is best matched to the way the
61 ** argument is handled internally and will deliver the optimum
62 ** resolution. The MJD method and the date & time methods are both
63 ** good compromises between resolution and convenience. For most
64 ** applications of this function the choice will not be at all
65 ** critical.
66 **
67 ** TT can be used instead of TDB without any significant impact on
68 ** accuracy.
69 **
70 ** 2) All the vectors are with respect to BCRS axes.
71 **
72 ** 3) This is one of several functions that inserts into the astrom
73 ** structure star-independent parameters needed for the chain of
74 ** astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
75 **
76 ** The various functions support different classes of observer and
77 ** portions of the transformation chain:
78 **
79 ** functions observer transformation
80 **
81 ** eraApcg eraApcg13 geocentric ICRS <-> GCRS
82 ** eraApci eraApci13 terrestrial ICRS <-> CIRS
83 ** eraApco eraApco13 terrestrial ICRS <-> observed
84 ** eraApcs eraApcs13 space ICRS <-> GCRS
85 ** eraAper eraAper13 terrestrial update Earth rotation
86 ** eraApio eraApio13 terrestrial CIRS <-> observed
87 **
88 ** Those with names ending in "13" use contemporary ERFA models to
89 ** compute the various ephemerides. The others accept ephemerides
90 ** supplied by the caller.
91 **
92 ** The transformation from ICRS to GCRS covers space motion,
93 ** parallax, light deflection, and aberration. From GCRS to CIRS
94 ** comprises frame bias and precession-nutation. From CIRS to
95 ** observed takes account of Earth rotation, polar motion, diurnal
96 ** aberration and parallax (unless subsumed into the ICRS <-> GCRS
97 ** transformation), and atmospheric refraction.
98 **
99 ** 4) The context structure astrom produced by this function is used by
100 ** eraAtciq* and eraAticq*.
101 **
102 ** Called:
103 ** eraApcs astrometry parameters, ICRS-GCRS, space observer
104 **
105 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
106 ** Derived, with permission, from the SOFA library. See notes at end of file.
107 */
108 {
109 /* Geocentric observer */
110  double pv[2][3] = { { 0.0, 0.0, 0.0 },
111  { 0.0, 0.0, 0.0 } };
112 
113 /* Compute the star-independent astrometry parameters. */
114  eraApcs(date1, date2, pv, ebpv, ehp, astrom);
115 
116 /* Finished. */
117 
118 }
119 /*----------------------------------------------------------------------
120 **
121 **
122 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
123 ** All rights reserved.
124 **
125 ** This library is derived, with permission, from the International
126 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
127 ** available from http://www.iausofa.org.
128 **
129 ** The ERFA version is intended to retain identical functionality to
130 ** the SOFA library, but made distinct through different function and
131 ** file names, as set out in the SOFA license conditions. The SOFA
132 ** original has a role as a reference standard for the IAU and IERS,
133 ** and consequently redistribution is permitted only in its unaltered
134 ** state. The ERFA version is not subject to this restriction and
135 ** therefore can be included in distributions which do not support the
136 ** concept of "read only" software.
137 **
138 ** Although the intent is to replicate the SOFA API (other than
139 ** replacement of prefix names) and results (with the exception of
140 ** bugs; any that are discovered will be fixed), SOFA is not
141 ** responsible for any errors found in this version of the library.
142 **
143 ** If you wish to acknowledge the SOFA heritage, please acknowledge
144 ** that you are using a library derived from SOFA, rather than SOFA
145 ** itself.
146 **
147 **
148 ** TERMS AND CONDITIONS
149 **
150 ** Redistribution and use in source and binary forms, with or without
151 ** modification, are permitted provided that the following conditions
152 ** are met:
153 **
154 ** 1 Redistributions of source code must retain the above copyright
155 ** notice, this list of conditions and the following disclaimer.
156 **
157 ** 2 Redistributions in binary form must reproduce the above copyright
158 ** notice, this list of conditions and the following disclaimer in
159 ** the documentation and/or other materials provided with the
160 ** distribution.
161 **
162 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
163 ** the International Astronomical Union nor the names of its
164 ** contributors may be used to endorse or promote products derived
165 ** from this software without specific prior written permission.
166 **
167 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
168 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
169 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
170 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
171 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
172 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
173 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
174 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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178 ** POSSIBILITY OF SUCH DAMAGE.
179 **
180 */
eraApcs
void eraApcs(double date1, double date2, double pv[2][3], double ebpv[2][3], double ehp[3], eraASTROM *astrom)
Definition: apcs.c:3
eraApcg
void eraApcg(double date1, double date2, double ebpv[2][3], double ehp[3], eraASTROM *astrom)
Definition: apcg.c:3