source: branches/FACT++_lidctrl_usb/erfa/src/ldsun.c@ 19875

Last change on this file since 19875 was 18711, checked in by tbretz, 10 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 4.4 KB
Line 
1#include "erfa.h"
2
3void eraLdsun(double p[3], double e[3], double em, double p1[3])
4/*
5** - - - - - - - - -
6** e r a L d s u n
7** - - - - - - - - -
8**
9** Deflection of starlight by the Sun.
10**
11** Given:
12** p double[3] direction from observer to star (unit vector)
13** e double[3] direction from Sun to observer (unit vector)
14** em double distance from Sun to observer (au)
15**
16** Returned:
17** p1 double[3] observer to deflected star (unit vector)
18**
19** Notes:
20**
21** 1) The source is presumed to be sufficiently distant that its
22** directions seen from the Sun and the observer are essentially
23** the same.
24**
25** 2) The deflection is restrained when the angle between the star and
26** the center of the Sun is less than a threshold value, falling to
27** zero deflection for zero separation. The chosen threshold value
28** is within the solar limb for all solar-system applications, and
29** is about 5 arcminutes for the case of a terrestrial observer.
30**
31** 3) The arguments p and p1 can be the same array.
32**
33** Called:
34** eraLd light deflection by a solar-system body
35**
36** Copyright (C) 2013-2016, NumFOCUS Foundation.
37** Derived, with permission, from the SOFA library. See notes at end of file.
38*/
39{
40 double em2, dlim;
41
42
43/* Deflection limiter (smaller for distant observers). */
44 em2 = em*em;
45 if ( em2 < 1.0 ) em2 = 1.0;
46 dlim = 1e-6 / (em2 > 1.0 ? em2 : 1.0);
47
48/* Apply the deflection. */
49 eraLd(1.0, p, p, e, em, dlim, p1);
50
51/* Finished. */
52
53}
54/*----------------------------------------------------------------------
55**
56**
57** Copyright (C) 2013-2016, NumFOCUS Foundation.
58** All rights reserved.
59**
60** This library is derived, with permission, from the International
61** Astronomical Union's "Standards of Fundamental Astronomy" library,
62** available from http://www.iausofa.org.
63**
64** The ERFA version is intended to retain identical functionality to
65** the SOFA library, but made distinct through different function and
66** file names, as set out in the SOFA license conditions. The SOFA
67** original has a role as a reference standard for the IAU and IERS,
68** and consequently redistribution is permitted only in its unaltered
69** state. The ERFA version is not subject to this restriction and
70** therefore can be included in distributions which do not support the
71** concept of "read only" software.
72**
73** Although the intent is to replicate the SOFA API (other than
74** replacement of prefix names) and results (with the exception of
75** bugs; any that are discovered will be fixed), SOFA is not
76** responsible for any errors found in this version of the library.
77**
78** If you wish to acknowledge the SOFA heritage, please acknowledge
79** that you are using a library derived from SOFA, rather than SOFA
80** itself.
81**
82**
83** TERMS AND CONDITIONS
84**
85** Redistribution and use in source and binary forms, with or without
86** modification, are permitted provided that the following conditions
87** are met:
88**
89** 1 Redistributions of source code must retain the above copyright
90** notice, this list of conditions and the following disclaimer.
91**
92** 2 Redistributions in binary form must reproduce the above copyright
93** notice, this list of conditions and the following disclaimer in
94** the documentation and/or other materials provided with the
95** distribution.
96**
97** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
98** the International Astronomical Union nor the names of its
99** contributors may be used to endorse or promote products derived
100** from this software without specific prior written permission.
101**
102** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
103** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
104** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
105** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
106** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
107** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
108** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
109** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
110** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
111** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
112** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
113** POSSIBILITY OF SUCH DAMAGE.
114**
115*/
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