TLE (Two-Line Element Set)
A TLE is the NORAD two-line format for satellite orbital elements — 69-character lines encoding catalog number, epoch, inclination, RAAN, eccentricity, and mean motion — still the standard way satellite tracking data circulates.
Decoding the two lines
Line 1 carries the catalog number, classification, international designator, epoch (year + day-of-year), and ballistic terms. Line 2 carries the orbital elements proper: inclination, right ascension of the ascending node, eccentricity (decimal point implied), argument of perigee, mean anomaly, and mean motion in revs/day — everything an SGP4 propagator needs to predict position. A mod-10 checksum ends each line.
From mean motion you derive the orbital period, and with eccentricity you get apogee and perigee — enough to classify an orbit as LEO, MEO, GEO, or highly elliptical at a glance.
The modern counterpart
CCSDS standardized the same data as XML/JSON Orbit Mean-Elements Messages (OMM/GP format) — self-describing fields instead of positional columns. Our converter bridges both directions: TLE/3LE files to OMM/GP JSON or CSV, batch-converting entire catalogs with checksum validation.
Related Standards
- •NORAD Two-Line Element set format
- •CCSDS 502.0-B-2 — OMM/GP (Orbit Data Messages)
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