📘 Definition
A TLE is a standardised text format that encodes a satellite's orbital parameters — including inclination, eccentricity, RAAN, argument of perigee, mean anomaly, and mean motion — at a specific epoch. Developed by NORAD in the 1960s, TLEs are the foundation of public satellite tracking. Orbital Radar uses TLEs propagated through the SGP4 algorithm to generate real-time positions for all tracked objects.
2 data + 1 name
Lines
6 Keplerian + drag
Elements Encoded
SGP4/SDP4
Propagator
Space-Track.org / CelesTrak
Source
Understanding TLE
TLE Accuracy & Limitations
TLEs are general perturbation elements — they model atmospheric drag and Earth oblateness but not solar radiation pressure, third-body gravity, or manoeuvres. Accuracy degrades over time: a fresh TLE is typically accurate to 1 km, but after a week the error can grow to tens of kilometres. High-drag objects (low LEO) degrade faster.
Where to Get TLEs
The primary source is Space-Track.org (US Space Force, requires free account) and CelesTrak (Dr. T.S. Kelso's aggregation service, no login required). Orbital Radar fetches from both sources multiple times daily.