SUBROUTINE iau_FK5HZ ( R5, D5, DATE1, DATE2, RH, DH ) *+ * - - - - - - - - - - * i a u _ F K 5 H Z * - - - - - - - - - - * * Transform an FK5 (J2000.0) star position into the system of the * Hipparcos catalogue, assuming zero Hipparcos proper motion. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * R5 d FK5 RA (radians), equinox J2000.0, at date * D5 d FK5 Dec (radians), equinox J2000.0, at date * DATE1,DATE2 d TDB date (Notes 1,2) * * Returned: * RH d Hipparcos RA (radians) * DH d Hipparcos Dec (radians) * * Notes: * * 1) This routine converts a star position from the FK5 system to * the Hipparcos system, in such a way that the Hipparcos proper * motion is zero. Because such a star has, in general, a non-zero * proper motion in the FK5 system, the routine requires the date * at which the position in the FK5 system was determined. * * 2) 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. * * 3) The FK5 to Hipparcos transformation is modeled as a pure * rotation and spin; zonal errors in the FK5 catalogue are * not taken into account. * * 4) The position returned by this routine is in the Hipparcos * reference system but at date DATE1+DATE2. * * 5) See also iau_FK52H, iau_H2FK5, iau_HFK5Z. * * Called: * iau_S2C spherical coordinates to unit vector * iau_FK5HIP FK5 to Hipparcos rotation and spin * iau_SXP multiply p-vector by scalar * iau_RV2M r-vector to r-matrix * iau_TRXP product of transpose of r-matrix and p-vector * iau_PXP vector product of two p-vectors * iau_C2S p-vector to spherical * iau_ANP normalize angle into range 0 to 2pi * * Reference: * * F.Mignard & M.Froeschle, Astron. Astrophys. 354, 732-739 (2000). * * This revision: 2012 September 5 * * SOFA release 2017-04-20 * * Copyright (C) 2017 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION R5, D5, DATE1, DATE2, RH, DH * Reference epoch (J2000.0), JD DOUBLE PRECISION DJ00 PARAMETER ( DJ00 = 2451545D0 ) * Days per Julian year DOUBLE PRECISION DJY PARAMETER ( DJY = 365.25D0 ) DOUBLE PRECISION T, P5E(3), R5H(3,3), S5H(3), VST(3), RST(3,3), : P5(3), PH(3), W DOUBLE PRECISION iau_ANP * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Interval from given date to fundamental epoch J2000.0 (JY). T = - ( ( DATE1-DJ00 ) + DATE2 ) / DJY * FK5 barycentric position vector. CALL iau_S2C ( R5, D5, P5E ) * FK5 to Hipparcos orientation matrix and spin vector. CALL iau_FK5HIP ( R5H, S5H ) * Accumulated Hipparcos wrt FK5 spin over that interval. CALL iau_SXP ( T, S5H, VST ) * Express the accumulated spin as a rotation matrix. CALL iau_RV2M ( VST, RST ) * Derotate the vector's FK5 axes back to date. CALL iau_TRXP ( RST, P5E, P5 ) * Rotate the vector into the Hipparcos system. CALL iau_RXP ( R5H, P5, PH ) * Hipparcos vector to spherical. CALL iau_C2S ( PH, W, DH ) RH = iau_ANP ( W ) * 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. All * variations, no matter how minor, must be explicitly marked as * such, as explained above. * * 4. You shall not cause the SOFA software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or * by inappropriate modification. * * 5. The SOFA software is provided "as is" and SOFA makes no warranty * as to its use or performance. SOFA does not and cannot warrant * the performance or results which the user may obtain by using the * SOFA software. SOFA makes no warranties, express or implied, as * to non-infringement of third party rights, merchantability, or * fitness for any particular purpose. In no event will SOFA be * liable to the user for any consequential, incidental, or special * damages, including any lost profits or lost savings, even if a * SOFA representative has been advised of such damages, or for any * claim by any third party. * * 6. 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