TLE¶

Source: AI/Tools/TleTools.cs

Parse a NORAD Two-Line Element set and propagate it with SGP4/SDP4. The TLE epoch is whatever is encoded in line 1; EvaluateTleAtEpoch re-propagates to an arbitrary epoch.

Mean vs. osculating elements

ParseTle returns Brouwer/Kozai mean elements consumed by SGP4/SDP4. These are not osculating Keplerian elements. Use EvaluateTleAtEpoch to obtain an osculating state vector.

ParseTle¶

Parse a TLE into its mean orbital elements plus drag terms.

Parameter	Type	Description
`line1`	string	First TLE line (begins with `1`)
`line2`	string	Second TLE line (begins with `2`)
`name`	string (optional)	Satellite name (line 0). Defaults to `UNNAMED`.

{
  "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"
}

Returns TleElements (mean a/e/i/RAAN/AOP/M, epoch, first and second derivatives of mean motion, ballistic coefficient).

EvaluateTleAtEpoch¶

Propagate the TLE with SGP4/SDP4 to a requested epoch and return the osculating state vector in the chosen frame. Earth is assumed as the central body.

Parameter	Type	Description
`line1`	string	First TLE line
`line2`	string	Second TLE line
`datetime`	ISO 8601 string	Epoch to evaluate at
`outputFrame`	`FramesEnum`	`TEME` is native to SGP4; `ICRF` is the standard inertial frame
`name`	string (optional)	Satellite name

Accuracy is approximate: typically ~1 km at the TLE epoch and degrading by ~1–3 km/day from there.

{
  "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"
}