Ephemeris trail
Build VSOP87
Truncating VSOP87
Testing VSOP87
Class organization
Reference frames
Handling frames
Handling precision
Handling time
Putting all together
Swiss Ephemeris
ELP 2000-82B
ELP 2000-82B is a theory built at the BDL by M. Chapront-Touze and J. Chapront to compute lunar ephemeris.
The purpose of this page is to explain how it was integrated to JEphem.

The original files can be found at ftp://ftp.bdl.fr/pub/ephem/moon/elp82.

ELP82b-2000 characteristics

Extract from file README :
    The constants of the subsequent lunar ephemeris are fitted to 
    the numerical integration DE200/LE200 of the Jet Propulsion Laboratory 
    and the arguments come from the semi-analytical theory ELP 2000-85.
The time scale is Barycentric Dynamical Time (TDB).

I couldn't find in BDL files neither the precision nor the validity interval of the theory.

Building process

From the BDL FTP directory, the files elp82b.ps (containing explanations) and elp82b_2 (containing the fortran routine) have been used to find out how to compute.
The data files have been transformed for JEphem's use by methods of BuildELP82.java (see source code or javadoc).

  • Tried to implement computation from elp82b.ps, but couldn't find my way out.
  • Translated the fortran routine elp82b_2 ; the resulting code is in class jephem.astro.solarsystem.ELP82
  • Tested to match the values given in the elp82b.ps ; precision not satisfactory.

  • The files are in directory JEphem/data/astro/planets/elp82