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Diffstat (limited to 'ast/erfa/aticq.c')
| -rw-r--r-- | ast/erfa/aticq.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/ast/erfa/aticq.c b/ast/erfa/aticq.c new file mode 100644 index 0000000..1e205b8 --- /dev/null +++ b/ast/erfa/aticq.c @@ -0,0 +1,199 @@ +#include "erfa.h" + +void eraAticq(double ri, double di, eraASTROM *astrom, + double *rc, double *dc) +/* +** - - - - - - - - - +** e r a A t i c q +** - - - - - - - - - +** +** Quick CIRS RA,Dec to ICRS astrometric place, given the star- +** independent astrometry parameters. +** +** Use of this function is appropriate when efficiency is important and +** where many star positions are all to be transformed for one date. +** The star-independent astrometry parameters can be obtained by +** calling one of the functions eraApci[13], eraApcg[13], eraApco[13] +** or eraApcs[13]. +** +** Given: +** ri,di double CIRS RA,Dec (radians) +** astrom eraASTROM* star-independent astrometry parameters: +** pmt double PM time interval (SSB, Julian years) +** eb double[3] SSB to observer (vector, au) +** eh double[3] Sun to observer (unit vector) +** em double distance from Sun to observer (au) +** v double[3] barycentric observer velocity (vector, c) +** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor +** bpn double[3][3] bias-precession-nutation matrix +** along double longitude + s' (radians) +** xpl double polar motion xp wrt local meridian (radians) +** ypl double polar motion yp wrt local meridian (radians) +** sphi double sine of geodetic latitude +** cphi double cosine of geodetic latitude +** diurab double magnitude of diurnal aberration vector +** eral double "local" Earth rotation angle (radians) +** refa double refraction constant A (radians) +** refb double refraction constant B (radians) +** +** Returned: +** rc,dc double ICRS astrometric RA,Dec (radians) +** +** Notes: +** +** 1) Only the Sun is taken into account in the light deflection +** correction. +** +** 2) Iterative techniques are used for the aberration and light +** deflection corrections so that the functions eraAtic13 (or +** eraAticq) and eraAtci13 (or eraAtciq) are accurate inverses; +** even at the edge of the Sun's disk the discrepancy is only about +** 1 nanoarcsecond. +** +** Called: +** eraS2c spherical coordinates to unit vector +** eraTrxp product of transpose of r-matrix and p-vector +** eraZp zero p-vector +** eraAb stellar aberration +** eraLdsun light deflection by the Sun +** eraC2s p-vector to spherical +** eraAnp normalize angle into range +/- pi +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + int j, i; + double pi[3], ppr[3], pnat[3], pco[3], w, d[3], before[3], r2, r, + after[3]; + + +/* CIRS RA,Dec to Cartesian. */ + eraS2c(ri, di, pi); + +/* Bias-precession-nutation, giving GCRS proper direction. */ + eraTrxp(astrom->bpn, pi, ppr); + +/* Aberration, giving GCRS natural direction. */ + eraZp(d); + for (j = 0; j < 2; j++) { + r2 = 0.0; + for (i = 0; i < 3; i++) { + w = ppr[i] - d[i]; + before[i] = w; + r2 += w*w; + } + r = sqrt(r2); + for (i = 0; i < 3; i++) { + before[i] /= r; + } + eraAb(before, astrom->v, astrom->em, astrom->bm1, after); + r2 = 0.0; + for (i = 0; i < 3; i++) { + d[i] = after[i] - before[i]; + w = ppr[i] - d[i]; + pnat[i] = w; + r2 += w*w; + } + r = sqrt(r2); + for (i = 0; i < 3; i++) { + pnat[i] /= r; + } + } + +/* Light deflection by the Sun, giving BCRS coordinate direction. */ + eraZp(d); + for (j = 0; j < 5; j++) { + r2 = 0.0; + for (i = 0; i < 3; i++) { + w = pnat[i] - d[i]; + before[i] = w; + r2 += w*w; + } + r = sqrt(r2); + for (i = 0; i < 3; i++) { + before[i] /= r; + } + eraLdsun(before, astrom->eh, astrom->em, after); + r2 = 0.0; + for (i = 0; i < 3; i++) { + d[i] = after[i] - before[i]; + w = pnat[i] - d[i]; + pco[i] = w; + r2 += w*w; + } + r = sqrt(r2); + for (i = 0; i < 3; i++) { + pco[i] /= r; + } + } + +/* ICRS astrometric RA,Dec. */ + eraC2s(pco, &w, dc); + *rc = eraAnp(w); + +/* 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. +** +*/ |