#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 ** **---------------------------------------------------------------------*/ }