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JPL Solar System Dynamics

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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 ( 1130619 asteroids, 3758 comets, 209 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.

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

 NOTE:    Although the web-interface to HORIZONS provides nearly all capabilities of the primary telnet interface (and email interface), it does not provide the following:
  • Small-body PARAMETER-MATCHING population searches
    (use the small-body search engine as an alternative)
  • Integration of USER-INPUT ORBITS
  • SPK BINARY FILE production

HORIZONS Documentation - (updated 2019-Dec-10)

Complete documentation is available in the following formats:

  • HTML document
  • PDF document (temporarily unavailable)
  • PostScript document (temporarily unavailable)
Documentation is also available on-line using the telnet interface to HORIZONS (simply type '?' from any prompt). New users of the web-interface to HORIZONS may want to consult this tutorial first. HORIZONS system news is also available describing recent changes and improvements.

Using the telnet Interface

The HORIZONS system can be accessed directly by connecting to "" via telnet port 6775. This will initiate a text-only "VT100" terminal session that accesses all HORIZONS functions. You will be taken through a series of prompts that will ask you questions needed to generate the desired information. To initiate such an interactive session from a UNIX/LINUX system command line, type:

icon  telnet 6775
Most MacOS and Windows telnet programs have a dialog box in which the port number (6775) can be entered. If after connecting to "" you are prompted for a login name (not necessary for HORIZONS), it means the port 6775 request was not passed along by the software on your end. Some Windows terminal software does not fully implement the telnet protocol and does not send port numbers, even if you enter them.

If your connection is refused, it is likely due to a firewall or security restriction at your end. In either case, please contact your local computer system administrator or consult your telnet program documentation if you need more help. Since no password or security information is exchanged, you may be able to request a firewall exception from your institution.

A HORIZONS terminal session can also be started from within a web-browser, by entering this URL in your browser:

If this URL does not open a session, your browser is not configured for telnet, and you will have to use the command-line method above, or web HTML or e-mail interfaces.

Using the email Interface

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 with the subject "BATCH-LONG". Alternatively, you can access the instructions via FTP.

IMPORTANT: Please be sure your email client is sending content as plain ASCII text. Failure to do so may result in no response from the system or an error message, even when your job-content appears perfect from within your email client. A helpful guide to suitably configure various email clients is available via this link.

FirstGov 2021-Sep-22 00:26 UT 
(server date/time)  
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