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slalib/nut.f

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+      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