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140 lines
3.9 KiB
Fortran
140 lines
3.9 KiB
Fortran
SUBROUTINE sla_AMPQK (RA, DA, AMPRMS, RM, DM)
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*+
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* - - - - - -
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* A M P Q K
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* - - - - - -
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*
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* Convert star RA,Dec from geocentric apparent to mean place
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*
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* The mean coordinate system is the post IAU 1976 system,
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* loosely called FK5.
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*
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* Use of this routine is appropriate when efficiency is important
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* and where many star positions are all to be transformed for
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* one epoch and equinox. The star-independent parameters can be
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* obtained by calling the sla_MAPPA routine.
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*
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* Given:
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* RA d apparent RA (radians)
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* DA d apparent Dec (radians)
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*
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* AMPRMS d(21) star-independent mean-to-apparent parameters:
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*
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* (1) time interval for proper motion (Julian years)
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* (2-4) barycentric position of the Earth (AU)
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* (5-7) heliocentric direction of the Earth (unit vector)
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* (8) (grav rad Sun)*2/(Sun-Earth distance)
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* (9-11) ABV: barycentric Earth velocity in units of c
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* (12) sqrt(1-v**2) where v=modulus(ABV)
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* (13-21) precession/nutation (3,3) matrix
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*
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* Returned:
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* RM d mean RA (radians)
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* DM d mean Dec (radians)
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*
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* References:
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* 1984 Astronomical Almanac, pp B39-B41.
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* (also Lederle & Schwan, Astron. Astrophys. 134,
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* 1-6, 1984)
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*
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* Note:
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*
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* Iterative techniques are used for the aberration and
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* light deflection corrections so that the routines
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* sla_AMP (or sla_AMPQK) and sla_MAP (or sla_MAPQK) are
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* accurate inverses; even at the edge of the Sun's disc
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* the discrepancy is only about 1 nanoarcsecond.
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*
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* Called: sla_DCS2C, sla_DIMXV, sla_DVDV, sla_DVN, sla_DCC2S,
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* sla_DRANRM
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*
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* P.T.Wallace Starlink 7 May 2000
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*
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* Copyright (C) 2000 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 RA,DA,AMPRMS(21),RM,DM
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INTEGER I,J
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DOUBLE PRECISION GR2E,AB1,EHN(3),ABV(3),P3(3),P2(3),
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: AB1P1,P1DV,P1DVP1,P1(3),W,PDE,PDEP1,P(3)
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DOUBLE PRECISION sla_DVDV,sla_DRANRM
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* Unpack scalar and vector parameters
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GR2E = AMPRMS(8)
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AB1 = AMPRMS(12)
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DO I=1,3
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EHN(I) = AMPRMS(I+4)
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ABV(I) = AMPRMS(I+8)
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END DO
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* Apparent RA,Dec to Cartesian
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CALL sla_DCS2C(RA,DA,P3)
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* Precession and nutation
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CALL sla_DIMXV(AMPRMS(13),P3,P2)
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* Aberration
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AB1P1 = AB1+1D0
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DO I=1,3
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P1(I) = P2(I)
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END DO
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DO J=1,2
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P1DV = sla_DVDV(P1,ABV)
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P1DVP1 = 1D0+P1DV
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W = 1D0+P1DV/AB1P1
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DO I=1,3
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P1(I) = (P1DVP1*P2(I)-W*ABV(I))/AB1
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END DO
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CALL sla_DVN(P1,P3,W)
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DO I=1,3
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P1(I) = P3(I)
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END DO
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END DO
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* Light deflection
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DO I=1,3
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P(I) = P1(I)
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END DO
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DO J=1,5
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PDE = sla_DVDV(P,EHN)
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PDEP1 = 1D0+PDE
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W = PDEP1-GR2E*PDE
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DO I=1,3
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P(I) = (PDEP1*P1(I)-GR2E*EHN(I))/W
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END DO
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CALL sla_DVN(P,P2,W)
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DO I=1,3
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P(I) = P2(I)
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END DO
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END DO
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* Mean RA,Dec
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CALL sla_DCC2S(P,RM,DM)
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RM = sla_DRANRM(RM)
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END
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