TLE propagation

NORAD Two-Line Elements are propagated with SGP4/SDP4. Accuracy is approximate — typically ~1 km at the TLE epoch, degrading at a few km/day from there.

Parse a TLE

{
  "name": "ISS (ZARYA)",
  "line1": "1 25544U 98067A   24001.50000000  .00016717  00000-0  10270-3 0  9990",
  "line2": "2 25544  51.6423 353.0312 0000493 320.8755  39.2360 15.49309423 25703"
}

Tool: ParseTle. Returns the mean Brouwer/Kozai elements consumed by SGP4 (semi-major axis, eccentricity, inclination, RAAN, argument of periapsis, mean anomaly), plus the epoch, the first/second derivative of mean motion, and the ballistic coefficient.

These are not osculating Keplerian elements

Do not feed ParseTle's output to ConvertKeplerianElementsToStateVector — you will get a meaningless state. Use EvaluateTleAtEpoch for an osculating state.

Propagate to an epoch

{
  "line1": "1 25544U 98067A   24001.50000000  .00016717  00000-0  10270-3 0  9990",
  "line2": "2 25544  51.6423 353.0312 0000493 320.8755  39.2360 15.49309423 25703",
  "datetime": "2024-01-15T12:00:00",
  "outputFrame": "ICRF"
}

Tool: EvaluateTleAtEpoch. Returns an osculating state vector in the requested frame.

TEME is the SGP4-native frame. ICRF is the standard inertial frame; the server applies the TEME → ICRF rotation for you. Use TEME only if you specifically need it (e.g. validation against another SGP4 implementation).

A short propagation cadence

For a series of states, call EvaluateTleAtEpoch repeatedly with different datetimes. There is no batched-TLE tool; the cost is dominated by the small SGP4 step itself.