SUBROUTINE iau_POM00 ( XP, YP, SP, RPOM ) *+ * - - - - - - - - - - - * i a u _ P O M 0 0 * - - - - - - - - - - - * * Form the matrix of polar motion for a given date, IAU 2000. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * XP,YP d coordinates of the pole (radians, Note 1) * SP d the TIO locator s' (radians, Note 2) * * Returned: * RPOM d(3,3) polar-motion matrix (Note 3) * * Notes: * * 1) XP and YP are the "coordinates of the pole", in radians, which * position the Celestial Intermediate Pole in the International * Terrestrial Reference System (see IERS Conventions 2003). In a * geocentric right-handed triad u,v,w, where the w-axis points at * the north geographic pole, the v-axis points towards the origin * of longitudes and the u axis completes the system, XP = +u and * YP = -v. * * 2) SP is the TIO locator s', in radians, which positions the * Terrestrial Intermediate Origin on the equator. It is obtained * from polar motion observations by numerical integration, and so is * in essence unpredictable. However, it is dominated by a secular * drift of about 47 microarcseconds per century, and so can be taken * into account by using s' = -47*t, where t is centuries since * J2000. The routine iau_SP00 implements this approximation. * * 3) The matrix operates in the sense V(TRS) = RPOM * V(CIP), meaning * that it is the final rotation when computing the pointing * direction to a celestial source. * * Called: * iau_IR initialize r-matrix to identity * iau_RZ rotate around Z-axis * iau_RY rotate around Y-axis * iau_RX rotate around X-axis * * Reference: * * McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), * IERS Technical Note No. 32, BKG (2004) * * This revision: 2006 October 10 * * Copyright (C) 2008 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION XP, YP, SP, RPOM(3,3) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Construct the matrix. CALL iau_IR ( RPOM ) CALL iau_RZ ( SP, RPOM ) CALL iau_RY ( -XP, RPOM ) CALL iau_RX ( -YP, RPOM ) * 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. 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