SUBROUTINE iau_HFK5Z ( RH, DH, DATE1, DATE2, R5, D5, DR5, DD5 )
*+
* - - - - - - - - - -
* i a u _ H F K 5 Z
* - - - - - - - - - -
*
* Transform a Hipparcos star position into FK5 J2000.0, assuming
* zero Hipparcos proper motion.
*
* This routine is part of the International Astronomical Union's
* SOFA (Standards of Fundamental Astronomy) software collection.
*
* Status: support routine.
*
* Given:
* RH d Hipparcos RA (radians)
* DH d Hipparcos Dec (radians)
* DATE1,DATE2 d TDB date (Note 1)
*
* Returned (all FK5, equinox J2000.0, date DATE1+DATE2):
* R5 d RA (radians)
* D5 d Dec (radians)
* DR5 d FK5 RA proper motion (rad/year, Note 4)
* DD5 d Dec proper motion (rad/year, Note 4)
*
* Notes:
*
* 1) The TDB date DATE1+DATE2 is a Julian Date, apportioned in any
* convenient way between the two arguments. For example,
* JD(TDB)=2450123.7 could be expressed in any of these ways, among
* others:
*
* DATE1 DATE2
*
* 2450123.7D0 0D0 (JD method)
* 2451545D0 -1421.3D0 (J2000 method)
* 2400000.5D0 50123.2D0 (MJD method)
* 2450123.5D0 0.2D0 (date & time method)
*
* The JD method is the most natural and convenient to use in
* cases where the loss of several decimal digits of resolution
* is acceptable. The J2000 method is best matched to the way
* the argument is handled internally and will deliver the
* optimum resolution. The MJD method and the date & time methods
* are both good compromises between resolution and convenience.
*
* 2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
*
* 3) The FK5 to Hipparcos transformation is modeled as a pure
* rotation and spin; zonal errors in the FK5 catalogue are
* not taken into account.
*
* 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 J2000.0
* reference system but at date DATE1+DATE2.
*
* 6) See also iau_FK52H, iau_H2FK5, iau_FK5ZHZ.
*
* Called:
* iau_S2C spherical coordinates to unit vector
* iau_FK5HIP FK5 to Hipparcos rotation and spin
* iau_RXP product of r-matrix and p-vector
* iau_SXP multiply p-vector by scalar
* iau_RXR product of two r-matrices
* iau_TRXP product of transpose of r-matrix and p-vector
* iau_PXP vector product of two p-vectors
* iau_PV2S pv-vector to spherical
* iau_ANP normalize angle into range 0 to 2pi
*
* Reference:
*
* F.Mignard & M.Froeschle, Astron. Astrophys. 354, 732-739 (2000).
*
* This revision: 2012 September 5
*
* SOFA release 2021-05-12
*
* Copyright (C) 2021 IAU SOFA Board. See notes at end.
*
*-----------------------------------------------------------------------
IMPLICIT NONE
DOUBLE PRECISION RH, DH, DATE1, DATE2, R5, D5, DR5, DD5
* Reference epoch (J2000.0), JD
DOUBLE PRECISION DJ00
PARAMETER ( DJ00 = 2451545D0 )
* Days per Julian year
DOUBLE PRECISION DJY
PARAMETER ( DJY = 365.25D0 )
DOUBLE PRECISION T, PH(3), R5H(3,3), S5H(3), SH(3), VST(3),
: RST(3,3), R5HT(3,3), PV5E(3,2), VV(3),
: W, R, V
DOUBLE PRECISION iau_ANP
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* Time interval from fundamental epoch J2000.0 to given date (JY).
T = ( ( DATE1-DJ00 ) + DATE2 ) / DJY
* Hipparcos barycentric position vector (normalized).
CALL iau_S2C ( RH, DH, PH )
* FK5 to Hipparcos orientation matrix and spin vector.
CALL iau_FK5HIP ( R5H, S5H )
* Rotate the spin into the Hipparcos system.
CALL iau_RXP ( R5H, S5H, SH )
* Accumulated Hipparcos wrt FK5 spin over that interval.
CALL iau_SXP ( T, S5H, VST )
* Express the accumulated spin as a rotation matrix.
CALL iau_RV2M ( VST, RST )
* Rotation matrix: accumulated spin, then FK5 to Hipparcos.
CALL iau_RXR ( R5H, RST, R5HT )
* De-orient & de-spin the Hipparcos position into FK5 J2000.0.
CALL iau_TRXP ( R5HT, PH, PV5E )
* Apply spin to the position giving a space motion.
CALL iau_PXP ( SH, PH, VV )
* De-orient & de-spin the Hipparcos space motion into FK5 J2000.0.
CALL iau_TRXP ( R5HT, VV, PV5E(1,2) )
* FK5 position/velocity pv-vector to spherical.
CALL iau_PV2S ( PV5E, W, D5, R, DR5, DD5, V )
R5 = iau_ANP ( W )
* Finished.
*+----------------------------------------------------------------------
*
* Copyright (C) 2021
* Standards Of Fundamental Astronomy Board
* of the International Astronomical Union.
*
* =====================
* SOFA Software License
* =====================
*
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*
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*
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*
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*
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*
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*-----------------------------------------------------------------------
END