#include "sofam.h"
void iauFk5hz(double r5, double d5, double date1, double date2,
double *rh, double *dh)
/*
** - - - - - - - - -
** i a u F k 5 h z
** - - - - - - - - -
**
** Transform an FK5 (J2000) star position into the system of the
** Hipparcos catalogue, assuming zero Hipparcos proper motion.
**
** This function is part of the International Astronomical Union's
** SOFA (Standards Of Fundamental Astronomy) software collection.
**
** Status: support function.
**
** Given:
** r5 double FK5 RA (radians), equinox J2000, at date
** d5 double FK5 Dec (radians), equinox J2000, at date
** date1,date2 double TDB date (Notes 1,2)
**
** Returned:
** rh double Hipparcos RA (radians)
** dh double Hipparcos Dec (radians)
**
** Notes:
**
** 1) This function converts a star position from the FK5 system to
** the Hipparcos system, in such a way that the Hipparcos proper
** motion is zero. Because such a star has, in general, a non-zero
** proper motion in the FK5 system, the function requires the date
** at which the position in the FK5 system was determined.
**
** 2) The TT date date1+date2 is a Julian Date, apportioned in any
** convenient way between the two arguments. For example,
** JD(TT)=2450123.7 could be expressed in any of these ways,
** among others:
**
** date1 date2
**
** 2450123.7 0.0 (JD method)
** 2451545.0 -1421.3 (J2000 method)
** 2400000.5 50123.2 (MJD method)
** 2450123.5 0.2 (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.
**
** 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 function returns those
** fictitious proper motions.
**
** 5) The position returned by this function is in the FK5 J2000
** reference system but at date date1+date2.
**
** 6) See also iauFk52h, iauH2fk5, iauHfk5z.
**
** Called:
** iauS2c spherical coordinates to unit vector
** iauFk5hip FK5 to Hipparcos rotation and spin
** iauSxp multiply p-vector by scalar
** iauRv2m r-vector to r-matrix
** iauTrxp product of transpose of r-matrix and p-vector
** iauPxp vector product of two p-vectors
** iauC2s p-vector to spherical
** iauAnp normalize angle into range 0 to 2pi
**
** Reference:
**
** F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739.
**
** This revision: 2008 May 24
**
** Copyright (C) 2008 IAU SOFA Review Board. See notes at end.
*/
{
double t, p5e[3], r5h[3][3], s5h[3], vst[3], rst[3][3], p5[3],
ph[3], w;
/* Interval from given date to fundamental epoch J2000.0 (JY). */
t = - ((date1 - DJ00) + date2) / DJY;
/* FK5 barycentric position vector. */
iauS2c(r5, d5, p5e);
/* FK5 to Hipparcos orientation matrix and spin vector. */
iauFk5hip(r5h, s5h);
/* Accumulated Hipparcos wrt FK5 spin over that interval. */
iauSxp(t, s5h, vst);
/* Express the accumulated spin as a rotation matrix. */
iauRv2m(vst, rst);
/* Derotate the vector's FK5 axes back to date. */
iauTrxp(rst, p5e, p5);
/* Rotate the vector into the Hipparcos system. */
iauRxp(r5h, p5, ph);
/* Hipparcos vector to spherical. */
iauC2s(ph, &w, dh);
*rh = iauAnp(w);
return;
/*-----------------------------------------------------------------------
**
** Copyright (C) 2008
** Standards Of Fundamental Astronomy Review Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS
** WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Review Board ("the Board").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and adapt the SOFA software and its
** algorithms for your own purposes and you may copy and distribute
** a resulting "derived work" to others on a world-wide, royalty-free
** basis, provided that the derived work complies with the following
** requirements:
**
** a) Your work shall be marked or carry a statement that it (i) uses
** routines and computations derived by you from software provided
** by SOFA under license to you; and (ii) does not contain
** software provided by SOFA or software that has been distributed
** by or endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon and/or differs from the
** original SOFA software.
**
** c) The name(s) of all routine(s) that you distribute shall differ
** from the SOFA names, even when the SOFA content has not been
** otherwise changed.
**
** d) The routine-naming prefix "iau" shall not be used.
**
** e) The origin of the SOFA components of your derived work must not
** be misrepresented; you must not claim that you wrote the
** original software, nor file a patent application for SOFA
** software or algorithms embedded in the SOFA software.
**
** f) These requirements must be reproduced intact in any source
** distribution and shall apply to anyone to whom you have granted
** a further right to modify the source code of your derived work.
**
** 4. In any published work or commercial products which includes
** results achieved by using the SOFA software, you shall acknowledge
** that the SOFA software was used in obtaining those results.
**
** 5. You shall not cause the SOFA software to be brought into
** disrepute, either by misuse, or use for inappropriate tasks, or by
** inappropriate modification.
**
** 6. The SOFA software is provided "as is" and the Board makes no
** warranty as to its use or performance. The Board does not and
** cannot warrant the performance or results which the user may obtain
** by using the SOFA software. The Board makes no warranties, express
** or implied, as to non-infringement of third party rights,
** merchantability, or fitness for any particular purpose. In no
** event will the Board be liable to the user for any consequential,
** incidental, or special damages, including any lost profits or lost
** savings, even if a Board representative has been advised of such
** damages, or for any claim by any third party.
**
** 7. The provision of any version of the SOFA software under the terms
** and conditions specified herein does not imply that future
** versions will also be made available under the same terms and
** conditions.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** Internet email: sofa@rl.ac.uk
** Postal address: IAU SOFA Center
** Rutherford Appleton Laboratory
** Chilton, Didcot, Oxon OX11 0QX
** United Kingdom
**
**---------------------------------------------------------------------*/
}