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 (in radians) of the Celestial * Intermediate Pole with respect to the International Terrestrial * Reference System (see IERS Conventions 2003), measured along the * meridians 0 and 90 deg west respectively. * * 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 * J2000.0. 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: 2020 October 31 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA 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) 2023 * 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. 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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