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#include "erfa.h"
void eraAb(double pnat[3], double v[3], double s, double bm1,
double ppr[3])
/*
** - - - - - -
** e r a A b
** - - - - - -
**
** Apply aberration to transform natural direction into proper
** direction.
**
** Given:
** pnat double[3] natural direction to the source (unit vector)
** v double[3] observer barycentric velocity in units of c
** s double distance between the Sun and the observer (au)
** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
**
** Returned:
** ppr double[3] proper direction to source (unit vector)
**
** Notes:
**
** 1) The algorithm is based on Expr. (7.40) in the Explanatory
** Supplement (Urban & Seidelmann 2013), but with the following
** changes:
**
** o Rigorous rather than approximate normalization is applied.
**
** o The gravitational potential term from Expr. (7) in
** Klioner (2003) is added, taking into account only the Sun's
** contribution. This has a maximum effect of about
** 0.4 microarcsecond.
**
** 2) In almost all cases, the maximum accuracy will be limited by the
** supplied velocity. For example, if the ERFA eraEpv00 function is
** used, errors of up to 5 microarcseconds could occur.
**
** References:
**
** Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
** the Astronomical Almanac, 3rd ed., University Science Books
** (2013).
**
** Klioner, Sergei A., "A practical relativistic model for micro-
** arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).
**
** Called:
** eraPdp scalar product of two p-vectors
**
** Copyright (C) 2013-2016, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
int i;
double pdv, w1, w2, r2, w, p[3], r;
pdv = eraPdp(pnat, v);
w1 = 1.0 + pdv/(1.0 + bm1);
w2 = ERFA_SRS/s;
r2 = 0.0;
for (i = 0; i < 3; i++) {
w = pnat[i]*bm1 + w1*v[i] + w2*(v[i] - pdv*pnat[i]);
p[i] = w;
r2 = r2 + w*w;
}
r = sqrt(r2);
for (i = 0; i < 3; i++) {
ppr[i] = p[i]/r;
}
/* Finished. */
}
/*----------------------------------------------------------------------
**
**
** Copyright (C) 2013-2016, NumFOCUS Foundation.
** All rights reserved.
**
** This library is derived, with permission, from the International
** Astronomical Union's "Standards of Fundamental Astronomy" library,
** available from http://www.iausofa.org.
**
** The ERFA version is intended to retain identical functionality to
** the SOFA library, but made distinct through different function and
** file names, as set out in the SOFA license conditions. The SOFA
** original has a role as a reference standard for the IAU and IERS,
** and consequently redistribution is permitted only in its unaltered
** state. The ERFA version is not subject to this restriction and
** therefore can be included in distributions which do not support the
** concept of "read only" software.
**
** Although the intent is to replicate the SOFA API (other than
** replacement of prefix names) and results (with the exception of
** bugs; any that are discovered will be fixed), SOFA is not
** responsible for any errors found in this version of the library.
**
** If you wish to acknowledge the SOFA heritage, please acknowledge
** that you are using a library derived from SOFA, rather than SOFA
** itself.
**
**
** TERMS AND CONDITIONS
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
**
** 1 Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
**
** 2 Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
**
** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
** the International Astronomical Union nor the names of its
** contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
** POSSIBILITY OF SUCH DAMAGE.
**
*/
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