Ephemera

One row per cycle, measured at the first instant of each operator file so the rows are comparable. A cycle marked scored with hindsight was matched against a catalogue snapshot fetched after it, because the cycle predates this project's catalogue feed. Its element sets already know what the satellite did during the file, so its numbers look better than they should and are not comparable with the rest. 7 of 51 scored cycles are in that state, and the count only falls from here.

Method: Public element set (Space-Track gp snapshot) propagated with SGP4 (skyfield 1.55, python-sgp4 2.27; TEME to GCRS by Skyfield, taken as J2000) and differenced against the operator-published trajectory (EME2000) at the file's own record epochs every 360 min. Distance in km; components in the operator's radial/in-track/cross-track frame; altitude is geocentric radius minus 6378.137 km; element age is evaluation epoch minus element-set epoch, signed. A comparison beyond 1000 km is counted as lost: the public set is not on the file's trajectory at all. at_file_start takes each satellite once, at the first epoch of its own file, which is the only cut comparable between cycles. Both inputs are predictions; the operator's includes planned trajectory changes the public set cannot know about.

Feed health for this cycle. The headline cycle, 764fb17cd429: 11,123 of 11,123 operator files scored. 0 have no entry in the public catalogue; 0 marked decayed; 0 failed to propagate; 0 unreadable; 0 no longer matching the record. Public element sets were a mean of 14.2 h old when the snapshot was taken (median 10.0 h, 90th percentile 28.5 h, 41 over 72 h). Averaged over every comparison, which run out to three days into the operator file, element age is 48.4 h: the difference is the file's own prediction horizon, not catalogue staleness. Space-Track: 161 snapshots held, last fetched 2026-09-17 20:10 UTC with 12,865 element sets. Poller heartbeat coverage over the last 24 h: 99.2%.