JPL's HORIZONS System

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 (42000+ asteroids and comets, 67 natural satellites, 9 planets, the Sun). HORIZONS is provided by the Solar System Dynamics Group of the Jet Propulsion Laboratory. This page is part of the JPL Solar System Dynamics WWW site.

The HORIZONS system can be accessed using any of the following methods:

WWW (see note below)
telnet (how to use the telnet method)
email (how to use the email method)

NOTE: The WWW interface to HORIZONS provides a subset of capabilities that should be sufficient for most observers needing topocentric ephemerides. Additional functions available only from the telnet and email interfaces include:

Small-body PARAMETER-MATCHING population searches
OSCULATING ELEMENT ephemerides
CARTESIAN VECTOR ephemerides
Integration of USER-INPUT ORBITS
SPK BINARY FILE production (telnet interface only)
Ephemerides for SITES ON BODIES OTHER THAN THE EARTH

HORIZONS Documentation

New users may want to consult the instructions for using the WWW interface to HORIZONS. Complete documentation (updated 2000 June 14) is available:

as an HTML document,
as a PostScript document, and
on-line from HORIZONS.

The latest HORIZONS system news is also available. Although the HORIZONS system will best serve most ephemeris requests, JPL's ephemeris files DE-200, DE-405, and DE-406 are available via ftp and CD-ROM.

Using the telnet Method

The HORIZONS system can be accessed using telnet to connect to host ssd.jpl.nasa.gov on port 6775. If the direct telnet link does not work on your browser, you may be able to connect manually. For example, from most UNIX systems you would type:

  telnet ssd.jpl.nasa.gov 6775

Most MacOS and Windows telnet programs have a dialog box in which the port number (6775) should be entered. If after connecting to "ssd.jpl.nasa.gov" you are prompted for a login name (which is not required for HORIZONS), your telnet port is probably not set to 6775. Please contact your local computer system administrator or consult your telnet program documentation if you need more help. If your connection is refused, either the maximum number of connections are being used, or the system is temporarily off line. In either case, please try again later.

Using the email Method

The HORIZONS system can be accessed using email to submit batch-style input files. Instructions on how to access the email server, including a complete detailed example, is available by sending an email message to horizons@ssd.jpl.nasa.gov with the subject ``BATCH-LONG''.

Credits/Awards

Contact: Webmaster (webmaster@ssd.jpl.nasa.gov)

Last modified: 2000 June 28 08:40