elp82b.h

/************************************************************************

LUNAR SOLUTION ELP2000-82B
by Chapront-Touze M., Chapront J.
ftp://ftp.imcce.fr/pub/ephem/moon/elp82b

I (Johannes Gajdosik) have just taken the Fortran code and data
obtained from above and used it to create this piece of software.

I can neigther allow nor forbid the usage of ELP2000-82B.
The copyright notice below covers not the works of
Chapront-Touze M. and Chapront J., but just my work,
that is the compilation and rearrangement of
the Fortran code and data obtained from above
into the software supplied in this file.


Copyright (c) 2005 Johannes Gajdosik

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

My implementation of ELP2000-82B has the following modifications compared to
the original Fortran code:
1) fundamentally rearrange the series into optimized instructions
   for fast calculation of the results
2) units are: julian day, AU

****************************************************************/


#ifndef _ELP82B_H_
#define _ELP82B_H_

#ifdef __cplusplus
extern "C" {
#endif

void GetElp82bCoor(double jd,double xyz[3]);

  /* Return the rectangular coordinates of the earths moon
     on the given julian date jd expressed in dynamical time (TAI+32.184s).
     The origin of the xyz-coordinates is the center of the earth.
     The reference frame is "dynamical equinox and ecliptic J2000",
     which is the reference frame in VSOP87 and VSOP87A.

     According to vsop87.doc VSOP87 coordinates can be transformed to FK5 by
       X       cos(psi) -sin(psi) 0   1        0         0   X
       Y     = sin(psi)  cos(psi) 0 * 0 cos(eps) -sin(eps) * Y
       Z FK5          0         0 1   0 sin(eps)  cos(eps)   Z VSOP87
     with psi = -0.0000275 degrees = -0.099 arcsec and
     eps = 23.4392803055556 degrees = 23d26m21.4091sec.

     http://ssd.jpl.nasa.gov/horizons_doc.html#frames says:
       "J2000" selects an Earth Mean-Equator and dynamical Equinox of
       Epoch J2000.0 inertial reference system, where the Epoch of J2000.0
       is the Julian date 2451545.0. "Mean" indicates nutation effects are
       ignored in the frame definition. The system is aligned with the
       IAU-sponsored J2000 frame of the Radio Source Catalog of the
       International Earth Rotational Service (ICRF).
       The ICRF is thought to differ from FK5 by at most 0.01 arcsec.

     From this I conclude that in the context of stellarium
     ICRF, J2000 and FK5 are the same, while the transformation
     ICRF <-> VSOP87 must be done with the matrix given above.
   */
     

#ifdef __cplusplus
};
#endif

#endif