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slalib/ampqk.f

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