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80 lines
2.4 KiB
Fortran
80 lines
2.4 KiB
Fortran
SUBROUTINE sla_PREBN (BEP0, BEP1, RMATP)
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*+
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* - - - - - -
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* P R E B N
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* - - - - - -
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*
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* Generate the matrix of precession between two epochs,
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* using the old, pre-IAU1976, Bessel-Newcomb model, using
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* Kinoshita's formulation (double precision)
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*
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* Given:
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* BEP0 dp beginning Besselian epoch
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* BEP1 dp ending Besselian epoch
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*
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* Returned:
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* RMATP dp(3,3) precession matrix
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*
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* The matrix is in the sense V(BEP1) = RMATP * V(BEP0)
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*
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* Reference:
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* Kinoshita, H. (1975) 'Formulas for precession', SAO Special
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* Report No. 364, Smithsonian Institution Astrophysical
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* Observatory, Cambridge, Massachusetts.
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*
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* Called: sla_DEULER
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*
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* P.T.Wallace Starlink 23 August 1996
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*
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* Copyright (C) 1996 Rutherford Appleton Laboratory
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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DOUBLE PRECISION BEP0,BEP1,RMATP(3,3)
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* Arc seconds to radians
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DOUBLE PRECISION AS2R
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PARAMETER (AS2R=0.484813681109535994D-5)
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DOUBLE PRECISION BIGT,T,TAS2R,W,ZETA,Z,THETA
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* Interval between basic epoch B1850.0 and beginning epoch in TC
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BIGT = (BEP0-1850D0)/100D0
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* Interval over which precession required, in tropical centuries
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T = (BEP1-BEP0)/100D0
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* Euler angles
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TAS2R = T*AS2R
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W = 2303.5548D0+(1.39720D0+0.000059D0*BIGT)*BIGT
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ZETA = (W+(0.30242D0-0.000269D0*BIGT+0.017996D0*T)*T)*TAS2R
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Z = (W+(1.09478D0+0.000387D0*BIGT+0.018324D0*T)*T)*TAS2R
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THETA = (2005.1125D0+(-0.85294D0-0.000365D0*BIGT)*BIGT+
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: (-0.42647D0-0.000365D0*BIGT-0.041802D0*T)*T)*TAS2R
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* Rotation matrix
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CALL sla_DEULER('ZYZ',-ZETA,THETA,-Z,RMATP)
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END
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