diff options
Diffstat (limited to 'ast/erfa/apci13.c')
| -rw-r--r-- | ast/erfa/apci13.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/ast/erfa/apci13.c b/ast/erfa/apci13.c new file mode 100644 index 0000000..c041652 --- /dev/null +++ b/ast/erfa/apci13.c @@ -0,0 +1,202 @@ +#include "erfa.h" + +void eraApci13(double date1, double date2, + eraASTROM *astrom, double *eo) +/* +** - - - - - - - - - - +** e r a A p c i 1 3 +** - - - - - - - - - - +** +** For a terrestrial observer, prepare star-independent astrometry +** parameters for transformations between ICRS and geocentric CIRS +** coordinates. The caller supplies the date, and ERFA models are used +** to predict the Earth ephemeris and CIP/CIO. +** +** The parameters produced by this function are required in the +** parallax, light deflection, aberration, and bias-precession-nutation +** parts of the astrometric transformation chain. +** +** Given: +** date1 double TDB as a 2-part... +** date2 double ...Julian Date (Note 1) +** +** Returned: +** 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 unchanged +** xpl double unchanged +** ypl double unchanged +** sphi double unchanged +** cphi double unchanged +** diurab double unchanged +** eral double unchanged +** refa double unchanged +** refb double unchanged +** eo double* equation of the origins (ERA-GST) +** +** 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) All the vectors are with respect to BCRS axes. +** +** 3) In cases where the caller wishes to supply his own Earth +** ephemeris and CIP/CIO, the function eraApci can be used instead +** of the present function. +** +** 4) This is one of several functions that inserts into the astrom +** structure star-independent parameters needed for the chain of +** astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed. +** +** The various functions support different classes of observer and +** portions of the transformation chain: +** +** functions observer transformation +** +** eraApcg eraApcg13 geocentric ICRS <-> GCRS +** eraApci eraApci13 terrestrial ICRS <-> CIRS +** eraApco eraApco13 terrestrial ICRS <-> observed +** eraApcs eraApcs13 space ICRS <-> GCRS +** eraAper eraAper13 terrestrial update Earth rotation +** eraApio eraApio13 terrestrial CIRS <-> observed +** +** Those with names ending in "13" use contemporary ERFA models to +** compute the various ephemerides. The others accept ephemerides +** supplied by the caller. +** +** The transformation from ICRS to GCRS covers space motion, +** parallax, light deflection, and aberration. From GCRS to CIRS +** comprises frame bias and precession-nutation. From CIRS to +** observed takes account of Earth rotation, polar motion, diurnal +** aberration and parallax (unless subsumed into the ICRS <-> GCRS +** transformation), and atmospheric refraction. +** +** 5) The context structure astrom produced by this function is used by +** eraAtciq* and eraAticq*. +** +** Called: +** eraEpv00 Earth position and velocity +** eraPnm06a classical NPB matrix, IAU 2006/2000A +** eraBpn2xy extract CIP X,Y coordinates from NPB matrix +** eraS06 the CIO locator s, given X,Y, IAU 2006 +** eraApci astrometry parameters, ICRS-CIRS +** eraEors equation of the origins, given NPB matrix and s +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double ehpv[2][3], ebpv[2][3], r[3][3], x, y, s; + + +/* Earth barycentric & heliocentric position/velocity (au, au/d). */ + (void) eraEpv00(date1, date2, ehpv, ebpv); + +/* Form the equinox based BPN matrix, IAU 2006/2000A. */ + eraPnm06a(date1, date2, r); + +/* Extract CIP X,Y. */ + eraBpn2xy(r, &x, &y); + +/* Obtain CIO locator s. */ + s = eraS06(date1, date2, x, y); + +/* Compute the star-independent astrometry parameters. */ + eraApci(date1, date2, ebpv, ehpv[0], x, y, s, astrom); + +/* Equation of the origins. */ + *eo = eraEors(r, s); + +/* 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. +** +*/ |