Keplerian Data Files for Satellite Tracking

Two Line Elements Data Files

A "two line elements" file is specially formatted ASCII data file containing satellite orbital information. It actually consists of three lines per satellite entry. The first line is the satellite name, the second and third are the Keplerian terms and other related data in a format used by the US Space Command (formerly NORAD).

Two line elements files which are more than about 2 weeks out of date for non-maneuvering satellites will generally not be accurate enough for visual spotting. Maneuvering satellites such as the Space Shuttle are another matter. You must obtain the latest two line element set to be reasonably accurate for maneuvering satellites.

Dedicated Home Pages

• Dr. T. S. Kelso's Celestrak. Look under [Current Data] & [100 (or so) Brightest] for the most common visual elements.
• From the Goddard Space Flight Center in Greenbelt Maryland:
  • NASA Orbital Information Group (Server 1) (primary).
  • NASA Orbital Information Group (Server 3) (alternate, when Server 1 is not available).

• The AMSAT SAREX Elements

Email List Servers

• If you would like to receive timely E-mail updates of Space Shuttle elements, you can subscribe to a list server from NASA Spacelink.

FTP Sites

• The Kilroy List (400k-compressed) located at JPL. These files are in UNIX compressed format (filename.Z). To uncompress the file on a PC platform, one needs the GZIP utility (like PKZIP). Once GZIP is installed, use the command line "gzip -ad filename" to expand the elements file for reading into a satellite orbit modeling program.
• Dr. T. S. Kelso's FTP TLE site for groups of TLE's according to interest.
• Dr. T. S. Kelso's FTP TLE site of [100 (or so) Brightest for the most easily visible grouping of satellites.