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SUBROUTINE sla_HFK5Z (RH,DH,EPOCH,R5,D5,DR5,DD5)
*+
* - - - - - -
* H F K 5 Z
* - - - - - -
*
* Transform a Hipparcos star position into FK5 J2000, assuming
* zero Hipparcos proper motion.
*
* (double precision)
*
* Given:
* RH d Hipparcos RA (radians)
* DH d Hipparcos Dec (radians)
* EPOCH d Julian epoch (TDB)
*
* Returned (all FK5, equinox J2000, epoch EPOCH):
* R5 d RA (radians)
* D5 d Dec (radians)
*
* Called: sla_DCS2C, sla_DAV2M, sla_DMXV, sla_DAV2M, sla_DMXM,
* sla_DIMXV, sla_DVXV, sla_DC62S, sla_DRANRM
*
* Notes:
*
* 1) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
*
* 2) The FK5 to Hipparcos transformation consists of a pure
* rotation and spin; zonal errors in the FK5 catalogue are
* not taken into account.
*
* 3) The published orientation and spin components are interpreted
* as "axial vectors". An axial vector points at the pole of the
* rotation and its length is the amount of rotation in radians.
*
* 4) It was the intention that Hipparcos should be a close
* approximation to an inertial frame, so that distant objects
* have zero proper motion; such objects have (in general)
* non-zero proper motion in FK5, and this routine returns those
* fictitious proper motions.
*
* 5) The position returned by this routine is in the FK5 J2000
* reference frame but at Julian epoch EPOCH.
*
* 6) See also sla_FK52H, sla_H2FK5, sla_FK5ZHZ.
*
* Reference:
*
* M.Feissel & F.Mignard, Astron. Astrophys. 331, L33-L36 (1998).
*
* P.T.Wallace Starlink 22 June 1999
*
* Copyright (C) 1999 Rutherford Appleton Laboratory
*-
IMPLICIT NONE
DOUBLE PRECISION RH,DH,EPOCH,R5,D5,DR5,DD5
DOUBLE PRECISION AS2R
PARAMETER (AS2R=0.484813681109535994D-5)
* FK5 to Hipparcos orientation and spin (radians, radians/year)
DOUBLE PRECISION EPX,EPY,EPZ
DOUBLE PRECISION OMX,OMY,OMZ
PARAMETER ( EPX = -19.9D-3 * AS2R,
: EPY = -9.1D-3 * AS2R,
: EPZ = +22.9D-3 * AS2R )
PARAMETER ( OMX = -0.30D-3 * AS2R,
: OMY = +0.60D-3 * AS2R,
: OMZ = +0.70D-3 * AS2R )
DOUBLE PRECISION PH(6),ORTN(3),R5H(3,3),S5(3),SH(3),T,VST(3),
: RST(3,3),R5HT(3,3),PV5E(6),VV(3),W,R,V
DOUBLE PRECISION sla_DRANRM
* Hipparcos barycentric position vector (normalized).
CALL sla_DCS2C(RH,DH,PH)
* FK5 to Hipparcos orientation matrix.
ORTN(1) = EPX
ORTN(2) = EPY
ORTN(3) = EPZ
CALL sla_DAV2M(ORTN,R5H)
* Hipparcos wrt FK5 spin vector.
S5(1) = OMX
S5(2) = OMY
S5(3) = OMZ
* Rotate the spin vector into the Hipparcos frame.
CALL sla_DMXV(R5H,S5,SH)
* Time interval from J2000 to epoch.
T = EPOCH-2000D0
* Axial vector: accumulated Hipparcos wrt FK5 spin over that interval.
VST(1) = OMX*T
VST(2) = OMY*T
VST(3) = OMZ*T
* Express the accumulated spin as a rotation matrix.
CALL sla_DAV2M(VST,RST)
* Rotation matrix: accumulated spin, then FK5 to Hipparcos.
CALL sla_DMXM(R5H,RST,R5HT)
* De-orient & de-spin the vector into FK5 J2000 at epoch.
CALL sla_DIMXV(R5HT,PH,PV5E)
CALL sla_DVXV(SH,PH,VV)
CALL sla_DIMXV(R5HT,VV,PV5E(4))
* FK5 position/velocity 6-vector to spherical.
CALL sla_DC62S(PV5E,W,D5,R,DR5,DD5,V)
R5 = sla_DRANRM(W)
END
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