SUBROUTINE sla_NUT (DATE, RMATN) *+ * - - - - * N U T * - - - - * * Form the matrix of nutation for a given date - Shirai & Fukushima * 2001 theory (double precision) * * Reference: * Shirai, T. & Fukushima, T., Astron.J. 121, 3270-3283 (2001). * * Given: * DATE d TDB (loosely ET) as Modified Julian Date * (=JD-2400000.5) * Returned: * RMATN d(3,3) nutation matrix * * Notes: * * 1 The matrix is in the sense v(true) = rmatn * v(mean) . * where v(true) is the star vector relative to the true equator and * equinox of date and v(mean) is the star vector relative to the * mean equator and equinox of date. * * 2 The matrix represents forced nutation (but not free core * nutation) plus corrections to the IAU~1976 precession model. * * 3 Earth attitude predictions made by combining the present nutation * matrix with IAU~1976 precession are accurate to 1~mas (with * respect to the ICRS) for a few decades around 2000. * * 4 The distinction between the required TDB and TT is always * negligible. Moreover, for all but the most critical applications * UTC is adequate. * * Called: sla_NUTC, sla_DEULER * * Last revision: 1 December 2005 * * Copyright P.T.Wallace. All rights reserved. * * License: * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program (see SLA_CONDITIONS); if not, write to the * Free Software Foundation, Inc., 59 Temple Place, Suite 330, * Boston, MA 02111-1307 USA * *- IMPLICIT NONE DOUBLE PRECISION DATE,RMATN(3,3) DOUBLE PRECISION DPSI,DEPS,EPS0 * Nutation components and mean obliquity CALL sla_NUTC(DATE,DPSI,DEPS,EPS0) * Rotation matrix CALL sla_DEULER('XZX',EPS0,-DPSI,-(EPS0+DEPS),RMATN) END