The JPL HORIZONS on-line solar system data and ephemeris computation service provides access to key solar system data and flexible production of highly accurate ephemerides for solar system objects ( 561485 asteroids, 3099 comets, 171 planetary satellites, 8 planets, the Sun, L1, L2, select spacecraft, and system barycenters ). HORIZONS is provided by the Solar System Dynamics Group of the Jet Propulsion Laboratory.