source: trunk/FACT++/erfa/src/atic13.c@ 20000

Last change on this file since 20000 was 18921, checked in by tbretz, 8 years ago
Updated to ERFA 1.4.0
File size: 6.3 KB
Line 
1#include "erfa.h"
2
3void 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) 2013-2017, 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) 2013-2017, 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*/
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