SUBROUTINE iau_LTP ( EPJ, RP ) *+ * - - - - - - - - * i a u _ L T P * - - - - - - - - * * Long-term precession matrix. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * EPJ d Julian epoch (TT) * * Returned: * RP d(3,3) precession matrix, J2000.0 to date * * Notes: * * 1) The matrix is in the sense * * P_date = RP x P_J2000, * * where P_J2000 is a vector with respect to the J2000.0 mean equator * and equinox and P_date is the same vector with respect to the * equator and equinox of epoch EPJ. * * 2) The Vondrak et al. (2011, 2012) 400 millennia precession model * agrees with the IAU 2006 precession at J2000.0 and stays within * 100 microarcseconds during the 20th and 21st centuries. It is * accurate to a few arcseconds throughout the historical period, * worsening to a few tenths of a degree at the end of the * +/- 200,000 year time span. * * Called: * iau_LTPEQU equator pole, long term * iau_LTPECL ecliptic pole, long term * iau_PXP vector product * iau_PN normalize vector * * References: * * Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession * expressions, valid for long time intervals, Astron.Astrophys. 534, * A22 * * Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession * expressions, valid for long time intervals (Corrigendum), * Astron.Astrophys. 541, C1 * * This revision: 2015 December 6 * * SOFA release 2019-07-22 * * Copyright (C) 2019 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION EPJ, RP(3,3) INTEGER I DOUBLE PRECISION PEQR(3), PECL(3), V(3), W, EQX(3) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Equator pole (bottom row of matrix). CALL iau_LTPEQU ( EPJ, PEQR ) * Ecliptic pole. CALL iau_LTPECL ( EPJ, PECL ) * Equinox (top row of matrix). CALL iau_PXP ( PEQR, PECL, V ) CALL iau_PN ( V, W, EQX ) * Middle row of matrix. CALL iau_PXP ( PEQR, EQX, V ) * Assemble the matrix. DO 1 I=1,3 RP(1,I) = EQX(I) RP(2,I) = V(I) RP(3,I) = PEQR(I) 1 CONTINUE * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2019 * 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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