SUBROUTINE iau_FK5HZ ( R5, D5, EPOCH1, EPOCH2, RH, DH ) *+ * - - - - - - - - - - * i a u _ F K 5 H Z * - - - - - - - - - - * * Transform an FK5 (J2000) star position into the frame 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 epoch * D5 d FK5 Dec (radians), equinox J2000, at epoch * EPOCH1,EPOCH2 d TDB epoch (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 epoch * at which the position in the FK5 system was determined. * * 2) The epoch EPOCH1+EPOCH2 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: * * EPOCH1 EPOCH2 * * 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 frame but at Julian epoch EPOCH1+EPOCH2. * * 6) See also iau_FK52H, iau_H2FK5, iau_HFK5Z. * * Called: * iau_S2C spherical to unit vector * iau_FK5HIP FK5 rotation and spin wrt to Hipparcos * iau_SXP product of scalar and p-vector * iau_RV2M r-vector to r-matrix * iau_TRXP product of transpose of r-matrix and p-vector * iau_PXP outer (=vector=cross) product of two p-vectors * iau_C2S unit vector to spherical * iau_ANP normalize radians to range 0 to 2pi * * Reference: * * M.Feissel & F.Mignard, Astron. Astrophys. 331, L33-L36 (1998). * * This revision: 2001 January 4 * * Copyright (C) 2001 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION R5, D5, EPOCH1, EPOCH2, RH, DH * Arcseconds to radians DOUBLE PRECISION DAS2R PARAMETER ( DAS2R = 4.848136811095359935899141D-6 ) * Reference epoch (J2000), JD DOUBLE PRECISION DJ0 PARAMETER ( DJ0 = 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 epoch to fundamental epoch J2000.0 (JY). T = - ( ( EPOCH1-DJ0 ) + EPOCH2 ) / 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 epoch. CALL iau_TRXP ( RST, P5E, P5 ) * Rotate the vector into the Hipparcos frame. CALL iau_RXP ( R5H, P5, PH ) * Hipparcos vector to spherical. CALL iau_C2S ( PH, W, DH ) RH = iau_ANP ( W ) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2001 * 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. The Software is made available free of charge for use by: * * a) private individuals for non-profit research; and * * b) non-profit educational, academic and research institutions. * * 3. Commercial use of the Software is specifically excluded from the * terms and conditions of this license. Commercial use of the * Software is subject to the prior written agreement of the Board on * terms to be agreed. * * 4. The provision of any version of the 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. * * 5. The user may modify the Software for his/her own purposes. The * user may distribute the modified software provided that the Board * is informed and that a copy of the modified software is made * available to the Board on request. All modifications made by the * user shall be clearly identified to show how the modified software * differs from the original Software, and the name(s) of the * affected routine(s) shall be changed. The original SOFA Software * License text must be present. * * 6. In any published work produced by the user and which includes * results achieved by using the Software, the user shall acknowledge * that the Software was used in producing the information contained * in such publication. * * 7. The user may incorporate or embed the Software into other software * products which he/she may then give away free of charge but not * sell provided the user makes due acknowledgement of the use which * he/she has made of the Software in creating such software * products. Any redistribution of the Software in this way shall be * made under the same terms and conditions under which the user * received it from the SOFA Center. * * 8. The user shall not cause the Software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 9. The Software is provided to the user "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 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. * * 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