diff options
Diffstat (limited to 'ast/erfa/ab.c')
| -rw-r--r-- | ast/erfa/ab.c | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/ast/erfa/ab.c b/ast/erfa/ab.c new file mode 100644 index 0000000..5d56656 --- /dev/null +++ b/ast/erfa/ab.c @@ -0,0 +1,137 @@ +#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. +** +*/ |