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 13 integers each.  (In the binary version, the
13th of each set is stored away from the first 12.)

The 13 triplets give information about the location, order and time-coverage of
the chebychev polynomials corresponding to the following 13 items:

       Mercury
       Venus
       Earth-Moon barycenter
       Mars 
       Jupiter 
       Saturn
       Uranus
       Neptune
       Pluto
       Moon (geocentric)
       Sun
       Nutations
       Librations

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.

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 : three Euler angles.

Planetary positions are stored in units of kilometers (TDB-compatible).
The nutations and librations are stored in units of radians.
