Technical
NORAD Catalog Number
A sequential number assigned to each tracked space object as it is catalogued, used as the primary key in two-line element sets.
The NORAD catalogue number (also called the satellite catalogue number) is assigned sequentially as objects are detected and catalogued by US space surveillance. It appears in two-line element sets and is the everyday identifier operators use to reference a specific object.
It complements the international designator: the catalogue number reflects the order of cataloguing, while the international designator encodes the launch.