This module computes positions and velocities of a celestial small body, from a
NASA SPICE SPK ephemeris kernel file of data type 1 (Modified Difference
Arrays).
See http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/spk.html

You can get SPK files for many solar system small bodies from HORIZONS system of
NASA/JPL.
See https://ssd.jpl.nasa.gov/?horizons

This module reads SPK files of data type 1, one of the types of binary SPK file.
At the point of Oct. 2018, HORIZONS system provides files of type 21 as binary
SPK files by default. You can get type 1 binary SPK file for celestial small
bodies through TELNET interface by answering back '1' for 'SPK file format'.