Notes

Coordinate System

The coordinate system used for the RA/Dec coordinate results is the IRCF (International Reference Celestial Frame), which is almost identical to J2000 with possible minute differences.

Validation

SatChecker has been validated with a preliminary set of observations done with DECam/Blanco by Guillermo Damke to verify that a given set of satellites appeared in the expected location at the expected time (Starlink Gen 2s). The results were consistent with the expected positions.

Satellite IDs

Satellites are assigned a temporary ID after launch, which can be used to identify them until they are assigned a permanent catalog number by Space Force. SpaceTrack and CelesTrak use different temporary numbering systems - SatChecker uses the ones from CelesTrak. Satellites can be found by searching by any of their IDs, including the temporary ones, but only the most recent ID will be displayed in the results.

TLE Dates

TLEs are only good for a maximum of two weeks as far as prediction accuracy goes, so using a TLE closest to the date requested gives the most accurate postion information. SatChecker will automatically select the most relevant TLE available for the requested date, but will still be constrained by the data_source parameter. This means that by default, Space-Track TLEs will be checked unless otherwise specified. This is relevant in two primary cases:

  1. If there is a supplemental TLE available from CelesTrak that is newer than what has been retrieved from Space-Track, using CelesTrak as the data source will provide the most accurate position information.

  2. Eventually, when archival TLEs are available, these will all be from Space-Track, so using CelesTrak as a data source will likely give a less timely result.

Other Notes

  • Results are limited to 1000 points per request.

  • Orbital predictions can be slightly less accurate right after satellite launch (and before they reach their final orbit), so those positions may be off by a bit temporarily.