SUBROUTINE iau_APCI13 ( DATE1, DATE2, ASTROM, EO ) *+ * - - - - - - - - - - - * i a u _ 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 SOFA models are * used to predict the Earth ephemeris and CIP/CIO. * * The parameters produced by this routine are required in the parallax, * light deflection, aberration, and bias-precession-nutation parts of * the astrometric transformation chain. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * DATE1 d TDB as a 2-part... * DATE2 d ...Julian Date (Note 1) * * Returned: * ASTROM d(30) star-independent astrometry parameters: * (1) PM time interval (SSB, Julian years) * (2-4) SSB to observer (vector, au) * (5-7) Sun to observer (unit vector) * (8) distance from Sun to observer (au) * (9-11) v: barycentric observer velocity (vector, c) * (12) sqrt(1-|v|^2): reciprocal of Lorenz factor * (13-21) bias-precession-nutation matrix * (22) unchanged * (23) unchanged * (24) unchanged * (25) unchanged * (26) unchanged * (27) unchanged * (28) unchanged * (29) unchanged * (30) unchanged * EO d 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 * * 2450123.7D0 0D0 (JD method) * 2451545D0 -1421.3D0 (J2000 method) * 2400000.5D0 50123.2D0 (MJD method) * 2450123.5D0 0.2D0 (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 routine 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 routine iau_APCI can be used instead of * the present routine. * * 4) This is one of several routines that inserts into the ASTROM * array star-independent parameters needed for the chain of * astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed. * * The various routines support different classes of observer and * portions of the transformation chain: * * routines observer transformation * * iau_APCG iau_APCG13 geocentric ICRS <-> GCRS * iau_APCI iau_APCI13 terrestrial ICRS <-> CIRS * iau_APCO iau_APCO13 terrestrial ICRS <-> observed * iau_APCS iau_APCS13 space ICRS <-> GCRS * iau_APER iau_APER13 terrestrial update Earth rotation * iau_APIO iau_APIO13 terrestrial CIRS <-> observed * * Those with names ending in "13" use contemporary SOFA 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 array ASTROM produced by this routine is used by * iau_ATCIQ* and iau_ATICQ*. * * Called: * iau_EPV00 Earth position and velocity * iau_PNM06A classical NPB matrix, IAU 2006/2000A * iau_BPN2XY extract CIP X,Y coordinates from NPB matrix * iau_S06 the CIO locator s, given X,Y, IAU 2006 * iau_APCI astrometry parameters, ICRS-CIRS * iau_EORS equation of the origins, given NPB matrix and s * * This revision: 2017 March 12 * * SOFA release 2017-04-20 * * Copyright (C) 2017 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION DATE1, DATE2, ASTROM(30), EO INTEGER J DOUBLE PRECISION PVH(3,2), PVB(3,2), R(3,3), X, Y, S DOUBLE PRECISION iau_S06, iau_EORS * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Earth barycentric & heliocentric position/velocity (au, au/d). CALL iau_EPV00 ( DATE1, DATE2, PVH, PVB, J ) * Form the equinox based BPN matrix, IAU 2006/2000A. CALL iau_PNM06A ( DATE1, DATE2, R ) * Extract CIP X,Y. CALL iau_BPN2XY ( R, X, Y ) * Obtain CIO locator s. S = iau_S06 ( DATE1, DATE2, X, Y ) * Compute the star-independent astrometry parameters. CALL iau_APCI ( DATE1, DATE2, PVB, PVH, X, Y, S, ASTROM ) * Equation of the origins. EO = iau_EORS ( R, S ) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2017 * Standards Of Fundamental Astronomy Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND * CONDITIONS WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Board ("SOFA"). * * 2. Permission is granted to anyone to use the SOFA software for any * purpose, including commercial applications, free of charge and * without payment of royalties, subject to the conditions and * restrictions listed below. * * 3. You (the user) may copy and distribute SOFA source code to others, * and use and adapt its code and algorithms in your own software, * on a world-wide, royalty-free basis. That portion of your * distribution that does not consist of intact and unchanged copies * of SOFA source code files is a "derived work" that must comply * with the following requirements: * * a) Your work shall be marked or carry a statement that it * (i) uses routines and computations derived by you from * software provided by SOFA under license to you; and * (ii) does not itself constitute software provided by and/or * endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon, contains and/or differs * from the original SOFA software. * * c) The names of all routines in your derived work shall not * include the prefix "iau" or "sofa" or trivial modifications * thereof such as changes of case. * * d) The origin of the SOFA components of your derived work must * not be misrepresented; you must not claim that you wrote the * original software, nor file a patent application for SOFA * software or algorithms embedded in the SOFA software. * * e) These requirements must be reproduced intact in any source * distribution and shall apply to anyone to whom you have * granted a further right to modify the source code of your * derived work. * * Note that, as originally distributed, the SOFA software is * intended to be a definitive implementation of the IAU standards, * and consequently third-party modifications are discouraged. 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The provision of any version of the SOFA software under the terms * and conditions specified herein does not imply that future * versions will also be made available under the same terms and * conditions. * * In any published work or commercial product which uses the SOFA * software directly, acknowledgement (see www.iausofa.org) is * appreciated. * * Correspondence concerning SOFA software should be addressed as * follows: * * By email: sofa@ukho.gov.uk * By post: IAU SOFA Center * HM Nautical Almanac Office * UK Hydrographic Office * Admiralty Way, Taunton * Somerset, TA1 2DN * United Kingdom * *----------------------------------------------------------------------- END