1 #include "erfa.h"
2
eraApci(double date1,double date2,double ebpv[2][3],double ehp[3],double x,double y,double s,eraASTROM * astrom)3 void eraApci(double date1, double date2,
4 double ebpv[2][3], double ehp[3],
5 double x, double y, double s,
6 eraASTROM *astrom)
7 /*
8 ** - - - - - - - -
9 ** e r a A p c i
10 ** - - - - - - - -
11 **
12 ** For a terrestrial observer, prepare star-independent astrometry
13 ** parameters for transformations between ICRS and geocentric CIRS
14 ** coordinates. The Earth ephemeris and CIP/CIO are supplied by the
15 ** caller.
16 **
17 ** The parameters produced by this function are required in the
18 ** parallax, light deflection, aberration, and bias-precession-nutation
19 ** parts of the astrometric transformation chain.
20 **
21 ** Given:
22 ** date1 double TDB as a 2-part...
23 ** date2 double ...Julian Date (Note 1)
24 ** ebpv double[2][3] Earth barycentric position/velocity (au, au/day)
25 ** ehp double[3] Earth heliocentric position (au)
26 ** x,y double CIP X,Y (components of unit vector)
27 ** s double the CIO locator s (radians)
28 **
29 ** Returned:
30 ** astrom eraASTROM* star-independent astrometry parameters:
31 ** pmt double PM time interval (SSB, Julian years)
32 ** eb double[3] SSB to observer (vector, au)
33 ** eh double[3] Sun to observer (unit vector)
34 ** em double distance from Sun to observer (au)
35 ** v double[3] barycentric observer velocity (vector, c)
36 ** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
37 ** bpn double[3][3] bias-precession-nutation matrix
38 ** along double unchanged
39 ** xpl double unchanged
40 ** ypl double unchanged
41 ** sphi double unchanged
42 ** cphi double unchanged
43 ** diurab double unchanged
44 ** eral double unchanged
45 ** refa double unchanged
46 ** refb double unchanged
47 **
48 ** Notes:
49 **
50 ** 1) The TDB date date1+date2 is a Julian Date, apportioned in any
51 ** convenient way between the two arguments. For example,
52 ** JD(TDB)=2450123.7 could be expressed in any of these ways, among
53 ** others:
54 **
55 ** date1 date2
56 **
57 ** 2450123.7 0.0 (JD method)
58 ** 2451545.0 -1421.3 (J2000 method)
59 ** 2400000.5 50123.2 (MJD method)
60 ** 2450123.5 0.2 (date & time method)
61 **
62 ** The JD method is the most natural and convenient to use in cases
63 ** where the loss of several decimal digits of resolution is
64 ** acceptable. The J2000 method is best matched to the way the
65 ** argument is handled internally and will deliver the optimum
66 ** resolution. The MJD method and the date & time methods are both
67 ** good compromises between resolution and convenience. For most
68 ** applications of this function the choice will not be at all
69 ** critical.
70 **
71 ** TT can be used instead of TDB without any significant impact on
72 ** accuracy.
73 **
74 ** 2) All the vectors are with respect to BCRS axes.
75 **
76 ** 3) In cases where the caller does not wish to provide the Earth
77 ** ephemeris and CIP/CIO, the function eraApci13 can be used instead
78 ** of the present function. This computes the required quantities
79 ** using other ERFA functions.
80 **
81 ** 4) This is one of several functions that inserts into the astrom
82 ** structure star-independent parameters needed for the chain of
83 ** astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
84 **
85 ** The various functions support different classes of observer and
86 ** portions of the transformation chain:
87 **
88 ** functions observer transformation
89 **
90 ** eraApcg eraApcg13 geocentric ICRS <-> GCRS
91 ** eraApci eraApci13 terrestrial ICRS <-> CIRS
92 ** eraApco eraApco13 terrestrial ICRS <-> observed
93 ** eraApcs eraApcs13 space ICRS <-> GCRS
94 ** eraAper eraAper13 terrestrial update Earth rotation
95 ** eraApio eraApio13 terrestrial CIRS <-> observed
96 **
97 ** Those with names ending in "13" use contemporary ERFA models to
98 ** compute the various ephemerides. The others accept ephemerides
99 ** supplied by the caller.
100 **
101 ** The transformation from ICRS to GCRS covers space motion,
102 ** parallax, light deflection, and aberration. From GCRS to CIRS
103 ** comprises frame bias and precession-nutation. From CIRS to
104 ** observed takes account of Earth rotation, polar motion, diurnal
105 ** aberration and parallax (unless subsumed into the ICRS <-> GCRS
106 ** transformation), and atmospheric refraction.
107 **
108 ** 5) The context structure astrom produced by this function is used by
109 ** eraAtciq* and eraAticq*.
110 **
111 ** Called:
112 ** eraApcg astrometry parameters, ICRS-GCRS, geocenter
113 ** eraC2ixys celestial-to-intermediate matrix, given X,Y and s
114 **
115 ** Copyright (C) 2013-2020, NumFOCUS Foundation.
116 ** Derived, with permission, from the SOFA library. See notes at end of file.
117 */
118 {
119
120 /* Star-independent astrometry parameters for geocenter. */
121 eraApcg(date1, date2, ebpv, ehp, astrom);
122
123 /* CIO based BPN matrix. */
124 eraC2ixys(x, y, s, astrom->bpn);
125
126 /* Finished. */
127
128 }
129 /*----------------------------------------------------------------------
130 **
131 **
132 ** Copyright (C) 2013-2020, NumFOCUS Foundation.
133 ** All rights reserved.
134 **
135 ** This library is derived, with permission, from the International
136 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
137 ** available from http://www.iausofa.org.
138 **
139 ** The ERFA version is intended to retain identical functionality to
140 ** the SOFA library, but made distinct through different function and
141 ** file names, as set out in the SOFA license conditions. The SOFA
142 ** original has a role as a reference standard for the IAU and IERS,
143 ** and consequently redistribution is permitted only in its unaltered
144 ** state. The ERFA version is not subject to this restriction and
145 ** therefore can be included in distributions which do not support the
146 ** concept of "read only" software.
147 **
148 ** Although the intent is to replicate the SOFA API (other than
149 ** replacement of prefix names) and results (with the exception of
150 ** bugs; any that are discovered will be fixed), SOFA is not
151 ** responsible for any errors found in this version of the library.
152 **
153 ** If you wish to acknowledge the SOFA heritage, please acknowledge
154 ** that you are using a library derived from SOFA, rather than SOFA
155 ** itself.
156 **
157 **
158 ** TERMS AND CONDITIONS
159 **
160 ** Redistribution and use in source and binary forms, with or without
161 ** modification, are permitted provided that the following conditions
162 ** are met:
163 **
164 ** 1 Redistributions of source code must retain the above copyright
165 ** notice, this list of conditions and the following disclaimer.
166 **
167 ** 2 Redistributions in binary form must reproduce the above copyright
168 ** notice, this list of conditions and the following disclaimer in
169 ** the documentation and/or other materials provided with the
170 ** distribution.
171 **
172 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
173 ** the International Astronomical Union nor the names of its
174 ** contributors may be used to endorse or promote products derived
175 ** from this software without specific prior written permission.
176 **
177 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
178 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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190 */
191