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The format was originally intended for [[punch card|punched card]]s, encoding a set of elements on two [[punched card#IBM 80-column format and character codes|standard 80-column cards]]. This format was eventually replaced by [[text file]]s as punch card systems became obsolete, with each set of elements written to two 69-column [[ASCII]] lines preceded by a title line. The [[United States Space Force]] tracks all detectable objects in Earth orbit, creating a corresponding TLE for each object, and makes publicly available TLEs for many of the space objects on the websites Space Track and Celestrak,<ref>{{cite web|url=https://www.space-track.org/|title=Introduction and sign in to Space-Track.Org|publisher=Space-track.org|access-date=28 November 2014}}</ref><ref>{{cite web|url=http://celestrak.com/|title=Celestrak homepage|publisher=Celestrak.com|access-date=28 November 2014}}</ref> holding back or obfuscating data on many military or [[Classified information|classified objects]]. The TLE format is a ''de facto'' standard for distribution of an Earth-orbiting object's orbital elements.
A TLE set may include a title line preceding the element data, so each listing may take up three lines in the file, in which case the TLE is referred to as a three-line element set (''3LE''), instead of a two-line element set (''2LE''). The title is not required, as each data line includes a unique object identifier code.
==History==
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