Two-line element set
NORAD's fixed-width text format for an object's orbit, read with the SGP4 model published in 1980; still the most shared orbital data, though its five-digit catalogue field overflowed and the CCSDS Orbit Mean-Elements Message has been used alongside it since 2020.
Part of the thread Who runs the registry? measures
builds on
- Satellite Catalog Number standard 1957 [src]
built upon by
- CelesTrak project 1985 [src]
- Space-Track project 2004 [src]
[?] Unconfirmed
- start: Date of Spacetrack Report #3, which published SGP4; the format itself is somewhat older.