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
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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