Tracking Programs and TLE Resources


Tracking Programs

Home Computer Satellite Tracking Program software is widely available for amateur satellite observers on the Internet or on BBSs, either commercially or as Shareware or Freeware. Most of these programs use Earth-centered orbital Keplerian Two Line Elements (TLEs). The TLE is a standard mathematical model to describe a satellite's orbit. TLEs are just one type of format for orbital elements. Another type is known as the AMSAT format and is mainly used for software that predicts amateur radio satellites.

Two Line Elements (TLEs) are processed by a computer tracking software program, yielding predictions for viewing time and position. The program determines the location of selected satellites above the horizon from a chosen observing location.

The satellite's celestial Right Ascension (RA) and Declination (Dec) coordinates and/or local coordinates of the satellite in terms of elevation (angle above the local horizon) and azimuth (true compass heading) during the pass are provided by the program at a frequency determined by the observer. Most of the tracking programs display these predicted coordinates and related information both graphically and in text format.

Some tracking program resources are :

Two-Line Elements (TLEs)

Naturally, tracking programs need accurate and recent data in order to generate accurate predictions. This data comes in the form of Keplerian or Two-Line Elements (TLEs). Groups of TLEs are also sometimes called "elsets".

TLE Satellite Resources

Government Resources is the primary distributor of U.S. Department of Defense (DoD) 2-line orbital elements and related data, replacing NASA Goddard Space Flight Center's Orbital Information Group (OIG), which permanently ceased operations on 2005 Mar 31.

NASA's Human Space Flight website provides predicted ISS and Shuttle elements, which take into account planned orbit manoeuvres.

Private Resources

There are private individuals and organizations not affiliated with government agencies that generate data on the Internet regarding Earth orbiting satellites.

  • Allen Thomson and others obtained historical TLEs from NASA/OIG, which Jonathan McDowell has archived on his Space home page. Some of these files are quite large and their size can be found at McDowell's directory. There is also a large index of catalog numbers to satellite common names.
  • Dr. T.S. Kelso's web site in the USA provides, in addition to a "30 day list", groupings of various types of satellites (i.e. nav, com, Iridium, weather, bright, etc.). Historical TLEs are provided for certain satellites.
  • Dave Cottle's Home Page in Australia
  • AMSAT's WWW server provides elements of satellites of interest primarily to radio amateurs, and an excellent explanation of the Keplerian elements format.
  • Ken Ernandes web site carries element sets.
  • Leo Barhorst maintains a current version of The RAE Table of Earth Satellites.
  • Willie Koorts' interesting South African homepage contains a handy small DOS utility called "extract". This program will allow the user to extract elements of his own choosing for custom grouping from larger files of elsets.

  • Satellite Prediction Services On The Internet

    The Heavens-Above site at Munich Germany provides predictions for bright satellites, including Mir, ISS and the shuttle, plus Iridium satellite flares. The user may either select a nearby town or city or input their own coordinates. In addition, the GSOC provides real-time simulated views of Mir above Earth for browsers with ActiveX capabilities.

    Alphonse Pouplier in Belgium provides prediction services for the Hubble Space Telescope and ISS.

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