1 #include "erfa.h"
2
eraAtic13(double ri,double di,double date1,double date2,double * rc,double * dc,double * eo)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) 2013-2014, 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
82 /* Star-independent astrometry parameters. */
83 eraApci13(date1, date2, &astrom, eo);
84
85 /* CIRS to ICRS astrometric. */
86 eraAticq(ri, di, &astrom, rc, dc);
87
88 /* Finished. */
89
90 }
91 /*----------------------------------------------------------------------
92 **
93 **
94 ** Copyright (C) 2013-2014, NumFOCUS Foundation.
95 ** All rights reserved.
96 **
97 ** This library is derived, with permission, from the International
98 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
99 ** available from http://www.iausofa.org.
100 **
101 ** The ERFA version is intended to retain identical functionality to
102 ** the SOFA library, but made distinct through different function and
103 ** file names, as set out in the SOFA license conditions. The SOFA
104 ** original has a role as a reference standard for the IAU and IERS,
105 ** and consequently redistribution is permitted only in its unaltered
106 ** state. The ERFA version is not subject to this restriction and
107 ** therefore can be included in distributions which do not support the
108 ** concept of "read only" software.
109 **
110 ** Although the intent is to replicate the SOFA API (other than
111 ** replacement of prefix names) and results (with the exception of
112 ** bugs; any that are discovered will be fixed), SOFA is not
113 ** responsible for any errors found in this version of the library.
114 **
115 ** If you wish to acknowledge the SOFA heritage, please acknowledge
116 ** that you are using a library derived from SOFA, rather than SOFA
117 ** itself.
118 **
119 **
120 ** TERMS AND CONDITIONS
121 **
122 ** Redistribution and use in source and binary forms, with or without
123 ** modification, are permitted provided that the following conditions
124 ** are met:
125 **
126 ** 1 Redistributions of source code must retain the above copyright
127 ** notice, this list of conditions and the following disclaimer.
128 **
129 ** 2 Redistributions in binary form must reproduce the above copyright
130 ** notice, this list of conditions and the following disclaimer in
131 ** the documentation and/or other materials provided with the
132 ** distribution.
133 **
134 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
135 ** the International Astronomical Union nor the names of its
136 ** contributors may be used to endorse or promote products derived
137 ** from this software without specific prior written permission.
138 **
139 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
140 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
141 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
142 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
143 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
144 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
145 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
146 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
147 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
148 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
149 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
150 ** POSSIBILITY OF SUCH DAMAGE.
151 **
152 */
153