• SPICE is the file format used
• some SPICE kernels are publicly available here.
  • EK — Events information
  • IL — Instrument information
  • PcK — Planetary cartographic and physical constants
  • SPK — Ephemeris subsystem
    • spk_l_* — launch
    • spk_c_* — cruise
  • CK — Orientation information
  • FK — Reference frames specifications
  • LSK — Leapseconds tabulation
  • SCLK — Spacecraft clock coefficients
• SPICE toolkit (incredibly useful, says ephemeris monkey boy)
• more info about SPICE files
  • forum after launch
• Keplerian elements for Earth and Mars: one