#include "erfa.h" void eraAtic13(double ri, double di, double date1, double date2, double *rc, double *dc, double *eo) /* ** - - - - - - - - - - ** e r a A t i c 1 3 ** - - - - - - - - - - ** ** Transform star RA,Dec from geocentric CIRS to ICRS astrometric. ** ** Given: ** ri,di double CIRS geocentric RA,Dec (radians) ** date1 double TDB as a 2-part... ** date2 double ...Julian Date (Note 1) ** ** Returned: ** rc,dc double ICRS astrometric RA,Dec (radians) ** eo double equation of the origins (ERA-GST, Note 4) ** ** Notes: ** ** 1) The TDB date date1+date2 is a Julian Date, apportioned in any ** convenient way between the two arguments. For example, ** JD(TDB)=2450123.7 could be expressed in any of these ways, among ** others: ** ** date1 date2 ** ** 2450123.7 0.0 (JD method) ** 2451545.0 -1421.3 (J2000 method) ** 2400000.5 50123.2 (MJD method) ** 2450123.5 0.2 (date & time method) ** ** The JD method is the most natural and convenient to use in cases ** where the loss of several decimal digits of resolution is ** acceptable. The J2000 method is best matched to the way the ** argument is handled internally and will deliver the optimum ** resolution. The MJD method and the date & time methods are both ** good compromises between resolution and convenience. For most ** applications of this function the choice will not be at all ** critical. ** ** TT can be used instead of TDB without any significant impact on ** accuracy. ** ** 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. ** ** 3) The available accuracy is better than 1 milliarcsecond, limited ** mainly by the precession-nutation model that is used, namely ** IAU 2000A/2006. Very close to solar system bodies, additional ** errors of up to several milliarcseconds can occur because of ** unmodeled light deflection; however, the Sun's contribution is ** taken into account, to first order. The accuracy limitations of ** the ERFA function eraEpv00 (used to compute Earth position and ** velocity) can contribute aberration errors of up to ** 5 microarcseconds. Light deflection at the Sun's limb is ** uncertain at the 0.4 mas level. ** ** 4) Should the transformation to (equinox based) J2000.0 mean place ** be required rather than (CIO based) ICRS coordinates, subtract the ** equation of the origins from the returned right ascension: ** RA = RI - EO. (The eraAnp function can then be applied, as ** required, to keep the result in the conventional 0-2pi range.) ** ** Called: ** eraApci13 astrometry parameters, ICRS-CIRS, 2013 ** eraAticq quick CIRS to ICRS astrometric ** ** Copyright (C) 2013-2014, NumFOCUS Foundation. ** Derived, with permission, from the SOFA library. See notes at end of file. */ { /* Star-independent astrometry parameters */ eraASTROM astrom; /* Star-independent astrometry parameters. */ eraApci13(date1, date2, &astrom, eo); /* CIRS to ICRS astrometric. */ eraAticq(ri, di, &astrom, rc, dc); /* Finished. */ } /*---------------------------------------------------------------------- ** ** ** Copyright (C) 2013-2014, 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. ** */