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70 lines
1.9 KiB
Fortran
70 lines
1.9 KiB
Fortran
SUBROUTINE sla_ECMAT (DATE, RMAT)
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*+
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* - - - - - -
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* E C M A T
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* - - - - - -
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*
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* Form the equatorial to ecliptic rotation matrix - IAU 1980 theory
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* (double precision)
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*
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* Given:
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* DATE dp TDB (loosely ET) as Modified Julian Date
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* (JD-2400000.5)
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* Returned:
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* RMAT dp(3,3) matrix
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*
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* Reference:
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* Murray,C.A., Vectorial Astrometry, section 4.3.
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*
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* Note:
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* The matrix is in the sense V(ecl) = RMAT * V(equ); the
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* equator, equinox and ecliptic are mean of date.
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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 DATE,RMAT(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 T,EPS0
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* Interval between basic epoch J2000.0 and current epoch (JC)
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T = (DATE-51544.5D0)/36525D0
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* Mean obliquity
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EPS0 = AS2R*
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: (84381.448D0+(-46.8150D0+(-0.00059D0+0.001813D0*T)*T)*T)
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* Matrix
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CALL sla_DEULER('X',EPS0,0D0,0D0,RMAT)
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END
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