FACT++  1.0
atic13.c
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1 #include "erfa.h"
2 
3 void eraAtic13(double ri, double di, double date1, double date2,
4  double *rc, double *dc, double *eo)
5 /*
6 ** - - - - - - - - - -
7 ** e r a A t i c 1 3
8 ** - - - - - - - - - -
9 **
10 ** Transform star RA,Dec from geocentric CIRS to ICRS astrometric.
11 **
12 ** Given:
13 ** ri,di double CIRS geocentric RA,Dec (radians)
14 ** date1 double TDB as a 2-part...
15 ** date2 double ...Julian Date (Note 1)
16 **
17 ** Returned:
18 ** rc,dc double ICRS astrometric RA,Dec (radians)
19 ** eo double equation of the origins (ERA-GST, Note 4)
20 **
21 ** Notes:
22 **
23 ** 1) The TDB date date1+date2 is a Julian Date, apportioned in any
24 ** convenient way between the two arguments. For example,
25 ** JD(TDB)=2450123.7 could be expressed in any of these ways, among
26 ** others:
27 **
28 ** date1 date2
29 **
30 ** 2450123.7 0.0 (JD method)
31 ** 2451545.0 -1421.3 (J2000 method)
32 ** 2400000.5 50123.2 (MJD method)
33 ** 2450123.5 0.2 (date & time method)
34 **
35 ** The JD method is the most natural and convenient to use in cases
36 ** where the loss of several decimal digits of resolution is
37 ** acceptable. The J2000 method is best matched to the way the
38 ** argument is handled internally and will deliver the optimum
39 ** resolution. The MJD method and the date & time methods are both
40 ** good compromises between resolution and convenience. For most
41 ** applications of this function the choice will not be at all
42 ** critical.
43 **
44 ** TT can be used instead of TDB without any significant impact on
45 ** accuracy.
46 **
47 ** 2) Iterative techniques are used for the aberration and light
48 ** deflection corrections so that the functions eraAtic13 (or
49 ** eraAticq) and eraAtci13 (or eraAtciq) are accurate inverses;
50 ** even at the edge of the Sun's disk the discrepancy is only about
51 ** 1 nanoarcsecond.
52 **
53 ** 3) The available accuracy is better than 1 milliarcsecond, limited
54 ** mainly by the precession-nutation model that is used, namely
55 ** IAU 2000A/2006. Very close to solar system bodies, additional
56 ** errors of up to several milliarcseconds can occur because of
57 ** unmodeled light deflection; however, the Sun's contribution is
58 ** taken into account, to first order. The accuracy limitations of
59 ** the ERFA function eraEpv00 (used to compute Earth position and
60 ** velocity) can contribute aberration errors of up to
61 ** 5 microarcseconds. Light deflection at the Sun's limb is
62 ** uncertain at the 0.4 mas level.
63 **
64 ** 4) Should the transformation to (equinox based) J2000.0 mean place
65 ** be required rather than (CIO based) ICRS coordinates, subtract the
66 ** equation of the origins from the returned right ascension:
67 ** RA = RI - EO. (The eraAnp function can then be applied, as
68 ** required, to keep the result in the conventional 0-2pi range.)
69 **
70 ** Called:
71 ** eraApci13 astrometry parameters, ICRS-CIRS, 2013
72 ** eraAticq quick CIRS to ICRS astrometric
73 **
74 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
75 ** Derived, with permission, from the SOFA library. See notes at end of file.
76 */
77 {
78 /* Star-independent astrometry parameters */
79  eraASTROM astrom;
80 
81 /* Star-independent astrometry parameters. */
82  eraApci13(date1, date2, &astrom, eo);
83 
84 /* CIRS to ICRS astrometric. */
85  eraAticq(ri, di, &astrom, rc, dc);
86 
87 /* Finished. */
88 
89 }
90 /*----------------------------------------------------------------------
91 **
92 **
93 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
94 ** All rights reserved.
95 **
96 ** This library is derived, with permission, from the International
97 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
98 ** available from http://www.iausofa.org.
99 **
100 ** The ERFA version is intended to retain identical functionality to
101 ** the SOFA library, but made distinct through different function and
102 ** file names, as set out in the SOFA license conditions. The SOFA
103 ** original has a role as a reference standard for the IAU and IERS,
104 ** and consequently redistribution is permitted only in its unaltered
105 ** state. The ERFA version is not subject to this restriction and
106 ** therefore can be included in distributions which do not support the
107 ** concept of "read only" software.
108 **
109 ** Although the intent is to replicate the SOFA API (other than
110 ** replacement of prefix names) and results (with the exception of
111 ** bugs; any that are discovered will be fixed), SOFA is not
112 ** responsible for any errors found in this version of the library.
113 **
114 ** If you wish to acknowledge the SOFA heritage, please acknowledge
115 ** that you are using a library derived from SOFA, rather than SOFA
116 ** itself.
117 **
118 **
119 ** TERMS AND CONDITIONS
120 **
121 ** Redistribution and use in source and binary forms, with or without
122 ** modification, are permitted provided that the following conditions
123 ** are met:
124 **
125 ** 1 Redistributions of source code must retain the above copyright
126 ** notice, this list of conditions and the following disclaimer.
127 **
128 ** 2 Redistributions in binary form must reproduce the above copyright
129 ** notice, this list of conditions and the following disclaimer in
130 ** the documentation and/or other materials provided with the
131 ** distribution.
132 **
133 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
134 ** the International Astronomical Union nor the names of its
135 ** contributors may be used to endorse or promote products derived
136 ** from this software without specific prior written permission.
137 **
138 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
139 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
140 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
141 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
142 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
143 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
144 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
145 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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149 ** POSSIBILITY OF SUCH DAMAGE.
150 **
151 */
eraAtic13
void eraAtic13(double ri, double di, double date1, double date2, double *rc, double *dc, double *eo)
Definition: atic13.c:3
eraApci13
void eraApci13(double date1, double date2, eraASTROM *astrom, double *eo)
Definition: apci13.c:3
eraAticq
void eraAticq(double ri, double di, eraASTROM *astrom, double *rc, double *dc)
Definition: aticq.c:3