SUBROUTINE iau_FK5HZ ( R5, D5, DATE1, DATE2, RH, DH ) *+ * - - - - - - - - - - * i a u _ F K 5 H Z * - - - - - - - - - - * * Transform an FK5 (J2000) 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, at date * D5 d FK5 Dec (radians), equinox J2000, 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 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) It was the intention that Hipparcos should be a close * approximation to an inertial frame, so that distant objects * have zero proper motion; such objects have (in general) * non-zero proper motion in FK5, and this routine returns those * fictitious proper motions. * * 5) The position returned by this routine is in the FK5 J2000 * reference system but at date DATE1+DATE2. * * 6) 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: 2008 May 24 * * Copyright (C) 2008 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION R5, D5, DATE1, DATE2, RH, DH * Reference epoch (J2000), 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) 2008 * Standards Of Fundamental Astronomy Review Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS * WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Review Board ("the Board"). * * 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 adapt the SOFA software and its * algorithms for your own purposes and you may copy and distribute * a resulting "derived work" to others on a world-wide, royalty-free * basis, provided that the derived work complies 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 contain * software provided by SOFA or software that has been distributed * by or endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon and/or differs from the * original SOFA software. * * c) The name(s) of all routine(s) that you distribute shall differ * from the SOFA names, even when the SOFA content has not been * otherwise changed. * * d) The routine-naming prefix "iau" shall not be used. * * e) 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. * * f) 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. * * 4. In any published work or commercial products which includes * results achieved by using the SOFA software, you shall acknowledge * that the SOFA software was used in obtaining those results. * * 5. You shall not cause the SOFA software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 6. The SOFA software is provided "as is" and the Board makes no * warranty as to its use or performance. The Board does not and * cannot warrant the performance or results which the user may obtain * by using the SOFA software. The Board 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 the Board be liable to the user for any consequential, * incidental, or special damages, including any lost profits or lost * savings, even if a Board representative has been advised of such * damages, or for any claim by any third party. * * 7. 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. * * Correspondence concerning SOFA software should be addressed as * follows: * * Internet email: sofa@rl.ac.uk * Postal address: IAU SOFA Center * Rutherford Appleton Laboratory * Chilton, Didcot, Oxon OX11 0QX * United Kingdom * *----------------------------------------------------------------------- END