Planetary Orbits & Ephemerides

Horizons

The Horizons service offers comprehensive access to the positions and other information on solar system objects, including the Sun, planets, planetary barycenters, planetary satellites, asteroids, comets, Lagrange Points, selected spacecraft, in a variety of forms and formats. It is the suggested means of obtaining such information for a wide range of analyses. Note that information on Pluto may be found on the Planetary Satellites/Orbits page, and that information for known Kuiper Belt Objects (KBOs), such as 486958 Arrokoth (the object investigated by the New Horizons mission, and originally and informally called “Ultima Thule”) may be found by specifying the minor planet designation (which for Arrokoth is 486958) in the Horizons system.

Formulae for Approximate Positions

Lower accuracy formulae for planetary positions have a number of important applications when one doesn’t need the full accuracy of an integrated ephemeris. Using these formulae with Keplerian elements for the planets provide suitable positions for such applications. Details for using this method are provided on the Approximate Positions of the Planets page.

Ephemerides

The JPL planetary and lunar ephemerides Development Ephemeris (DE) series includes the positions of the Sun, the barycenters of eight planetary systems, the Moon, the Pluto system barycenter, and lunar libration angles, as well as their associated velocities. Ephemerides are generally created to support spacecraft missions to the planets. New ephemerides are generated periodically to include new data and refine the dynamical models.

The JPL planetary and lunar ephemerides export information file contains a detailed description of the different ephemeris versions available as well as the links from which the ephemeris files can be downloaded. The use of these ephemeris files is recommended only for professionals whose needs are not readily met by the Horizons system. Alternatively, you may use the NAIF SPICE toolkit and planetary ephemerides in SPK format from JPL’s NAIF website.