This is an encore presentation of David Vallado's Expert Exchange presentation at the 2007 AGI User Exchange.
The U.S. Air Force has maintained a catalogue of orbiting objects since the launch of Sputnik in 1957. Maintaining this catalogue on the early computers was a significant challenge, and much research ensued on various theories of orbital motion that could be used for the efficient prediction of satellite motion. The selected theory, Simplified General Perturbations (SGP4), was well documented over the years, most recently in a comprehensive report titled Revisiting Spacetrack Report #3 (Vallado, Crawford, Hujsak, Kelso, AIAA 2006-6753). The availability of Two Line Element (TLE) data for SGP4 from AFSPC represents a valuable historical resource for analyses and some operational applications. As such, the generation of TLEs by AFSPC is of interest, as are methods for end users to generate accurate TLEs for exchange with other users. Detailed documentation covering the generation of TLEs and the associated methods of orbital element format conversion are not very common, so it is the aim of this presentation to collect the relevant information and provide insight into the process with specific examples.