TLE-tools is a small library to work with two-line element
set files.
The purpose of the library is to parse TLE sets into convenient TLE structures.
From Wikipedia:
A two-line element set (TLE) is a data format encoding a list of orbital elements of an Earth-orbiting object for a given point in time, the epoch. The TLE data representation is specific to the simplified perturbations models (SGP, SGP4, SDP4, SGP8 and SDP8), so any algorithm using a TLE as a data source must implement one of the SGP models to correctly compute the state at a time of interest. TLEs can describe the trajectories only of Earth-orbiting objects.
Example:
ISS (ZARYA)
1 25544U 98067A 19249.04864348 .00001909 00000-0 40858-4 0 9990
2 25544 51.6464 320.1755 0007999 10.9066 53.2893 15.50437522187805
Some more or less complete TLE format specifications can be found on the following websites: