File Coverage

erfasrc/src/ld.c

Criterion	Covered	Total	%
statement	0	10	0.0
branch	0	6	0.0
condition			n/a
subroutine			n/a
pod			n/a
total	0	16	0.0

line	stmt	bran	code
1			#include "erfa.h"
2
3	0		void eraLd(double bm, double p[3], double q[3], double e[3],
4			double em, double dlim, double p1[3])
5			/*
6			** - - - - - -
7			** e r a L d
8			** - - - - - -
9			**
10			** Apply light deflection by a solar-system body, as part of
11			** transforming coordinate direction into natural direction.
12			**
13			** Given:
14			** bm double mass of the gravitating body (solar masses)
15			** p double[3] direction from observer to source (unit vector)
16			** q double[3] direction from body to source (unit vector)
17			** e double[3] direction from body to observer (unit vector)
18			** em double distance from body to observer (au)
19			** dlim double deflection limiter (Note 4)
20			**
21			** Returned:
22			** p1 double[3] observer to deflected source (unit vector)
23			**
24			** Notes:
25			**
26			** 1) The algorithm is based on Expr. (70) in Klioner (2003) and
27			** Expr. (7.63) in the Explanatory Supplement (Urban & Seidelmann
28			** 2013), with some rearrangement to minimize the effects of machine
29			** precision.
30			**
31			** 2) The mass parameter bm can, as required, be adjusted in order to
32			** allow for such effects as quadrupole field.
33			**
34			** 3) The barycentric position of the deflecting body should ideally
35			** correspond to the time of closest approach of the light ray to
36			** the body.
37			**
38			** 4) The deflection limiter parameter dlim is phi^2/2, where phi is
39			** the angular separation (in radians) between source and body at
40			** which limiting is applied. As phi shrinks below the chosen
41			** threshold, the deflection is artificially reduced, reaching zero
42			** for phi = 0.
43			**
44			** 5) The returned vector p1 is not normalized, but the consequential
45			** departure from unit magnitude is always negligible.
46			**
47			** 6) The arguments p and p1 can be the same array.
48			**
49			** 7) To accumulate total light deflection taking into account the
50			** contributions from several bodies, call the present function for
51			** each body in succession, in decreasing order of distance from the
52			** observer.
53			**
54			** 8) For efficiency, validation is omitted. The supplied vectors must
55			** be of unit magnitude, and the deflection limiter non-zero and
56			** positive.
57			**
58			** References:
59			**
60			** Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
61			** the Astronomical Almanac, 3rd ed., University Science Books
62			** (2013).
63			**
64			** Klioner, Sergei A., "A practical relativistic model for micro-
65			** arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).
66			**
67			** Called:
68			** eraPdp scalar product of two p-vectors
69			** eraPxp vector product of two p-vectors
70			**
71			** Copyright (C) 2013-2019, NumFOCUS Foundation.
72			** Derived, with permission, from the SOFA library. See notes at end of file.
73			*/
74			{
75			int i;
76			double qpe[3], qdqpe, w, eq[3], peq[3];
77
78
79			/* q . (q + e). */
80	0	0	for (i = 0; i < 3; i++) {
81	0		qpe[i] = q[i] + e[i];
82			}
83	0		qdqpe = eraPdp(q, qpe);
84
85			/* 2 x G x bm / ( em x c^2 x ( q . (q + e) ) ). */
86	0	0	w = bm * ERFA_SRS / em / ERFA_GMAX(qdqpe,dlim);
87
88			/* p x (e x q). */
89	0		eraPxp(e, q, eq);
90	0		eraPxp(p, eq, peq);
91
92			/* Apply the deflection. */
93	0	0	for (i = 0; i < 3; i++) {
94	0		p1[i] = p[i] + w*peq[i];
95			}
96
97			/* Finished. */
98
99	0		}
100			/*----------------------------------------------------------------------
101			**
102			**
103			** Copyright (C) 2013-2019, NumFOCUS Foundation.
104			** All rights reserved.
105			**
106			** This library is derived, with permission, from the International
107			** Astronomical Union's "Standards of Fundamental Astronomy" library,
108			** available from http://www.iausofa.org.
109			**
110			** The ERFA version is intended to retain identical functionality to
111			** the SOFA library, but made distinct through different function and
112			** file names, as set out in the SOFA license conditions. The SOFA
113			** original has a role as a reference standard for the IAU and IERS,
114			** and consequently redistribution is permitted only in its unaltered
115			** state. The ERFA version is not subject to this restriction and
116			** therefore can be included in distributions which do not support the
117			** concept of "read only" software.
118			**
119			** Although the intent is to replicate the SOFA API (other than
120			** replacement of prefix names) and results (with the exception of
121			** bugs; any that are discovered will be fixed), SOFA is not
122			** responsible for any errors found in this version of the library.
123			**
124			** If you wish to acknowledge the SOFA heritage, please acknowledge
125			** that you are using a library derived from SOFA, rather than SOFA
126			** itself.
127			**
128			**
129			** TERMS AND CONDITIONS
130			**
131			** Redistribution and use in source and binary forms, with or without
132			** modification, are permitted provided that the following conditions
133			** are met:
134			**
135			** 1 Redistributions of source code must retain the above copyright
136			** notice, this list of conditions and the following disclaimer.
137			**
138			** 2 Redistributions in binary form must reproduce the above copyright
139			** notice, this list of conditions and the following disclaimer in
140			** the documentation and/or other materials provided with the
141			** distribution.
142			**
143			** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
144			** the International Astronomical Union nor the names of its
145			** contributors may be used to endorse or promote products derived
146			** from this software without specific prior written permission.
147			**
148			** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
149			** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
150			** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
151			** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
152			** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
153			** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
154			** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
155			** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
156			** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
157			** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
158			** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
159			** POSSIBILITY OF SUCH DAMAGE.
160			**
161			*/