Here is an overview of my Fortran planetary ephemeris service,
implemented in subroutine ephem.f.

This subroutine provides the position and velocity of any of the
nine planets or Moon.  The eight planets Mercury through Neptune
use the "VSOP87" theory, whereas Pluto and the Moon are handled
by separate modules, using different theories.

The data which are required by these subroutines are all contained
in memory--no files are used.

The result may be obtained as either a true geometric position or
apparent position (viewed from the Earth).  The reference frame
may be either equatorial (ECI), ecliptic, or heliocentric, and
the coordinate system may be either spherical or rectangular.
(The result type is selected by input parameters.)

Here is the subroutine call tree (with a brief explanation of
each called subroutine or function):

    ephem (the top-level subroutine described above)

        ut2td -- convert Universal Time to Dynamic Time

        hcpvd -- obtain the true heliocentric position and
            velocity of one of the 8 planets, using the VSOP87D
            theory (P. Bretagnon and G. Francou, Astron. Astrophys.
            v. 202 (1988), pp. 309-315).

            vsop87 -- block data subprogram holding the 
                harmonic series coefficients of the VSOP87D
                theory.  (This subroutine is actually created
                by a separate stand-alone Fortran main program,
                make_vsop87.f, which reads from the "D" coefficient
                files obtained from the VSOP87 author's anonymous
                ftp site.  A significant portion of the "total
                algorithm" is embodied in this program.

            pluto -- provides the heliocentric true or apparent
                position of Pluto (using the algorithm of J. Meeus
                in "Astronomical Algorithms", 2nd ed., Willmann-Bell,
                1998).

        sphxyz -- convert between spherical and rectangular
            coordinates.

        moonpv -- provides the true geocentric position and velocity
            of the Moon, using the theory of M. Chapront-Touze and
            J. Chapront, "Lunar Tables and Programs from 4000 B.C.
            to A.D. 8000", Willmann-Bell, 1991.

        fk5 -- transform VSOP87 theory to the standard FK5 system.

        nutate -- provide nutation corrections to the ecliptic
            longitude and obliquity of the ecliptic.

        obliq -- provide the true obliquity of the ecliptic.

        equecl -- convert between the equatorial (ECI) and ecliptic
            reference frames.

I have a make file (for Solaris) which creates a shareable object
library which may be used by Fortran, C, or IDL clients.  A different
make file is required to create a shareable object library accessible
by Java JNI clients.  I also have IDL and Java interfaces to ephem.f
(and some other useful astronomical services).  A documentation file,
astron.doc, which describes all of the services available in my
astronomy library, is attached.