INTERNAL FORMAT OF THE EPHEMERIS FILES
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On the first record of an export binary file or in the "GROUP 1050 of the ascii
"header", there are 3 sets of 15 integers each.  (Older versions have only the first 13
integers in each set)

The 15 triplets give information about the location, order and time-coverage of
the chebychev polynomials corresponding to the following 15 items:

       Mercury
       Venus
       Earth-Moon barycenter
       Mars 
       Jupiter 
       Saturn
       Uranus
       Neptune
       Pluto
       Moon (geocentric)
       Sun
       Earth Nutations in longitude and obliquity (IAU 1980 model)
       Lunar mantle libration
       Lunar mantle angular velocity
       TT-TDB (at geocenter)

Word (1,i) is the starting location in each data record of the chebychev 
coefficients belonging to the ith item.  Word (2,i) is the number of chebychev 
coefficients per component of the ith item, and Word (3,i) is the number of 
complete sets of coefficients in each data record for the ith item.

Items not stored on the ascii files have 0 coefficients [Word (3,i)].

Data Records ("GROUP 1070")

These records contain the actual ephemeris data in the form of chebychev 
polynomials.

The first two double precision words in each data record contain

         Julian date of earliest data in record.
         Julian date of latest data in record.

The remaining data are chebychev position coefficients for each component of 
each body on the tape.  The chebychev coefficients for the planets represent 
the solar system barycentric positions of the centers of the planetary systems.

There are three Cartesian components (x, y, z), for each of the items #1-11; 
there are two components for the 12th item, nutations : d(psi) and d(epsilon);
there are three components for the 13th item, librations : phi, theta, psi;
there are three components for the 14th item, mantle omega_x,omega_y,omega_z;
there is one component for the 17th item, TT-TDB.

Planetary positions are stored in units of kilometers (TDB-compatible).
The nutations and librations are stored in units of radians.
The mantle angular velocities are stored in radians/day.
TT-TDB is stored in seconds.