Satellite Catalog Number

The Satellite Catalog Number (SATCAT, also known as NORAD (North American Aerospace Defense) Catalog Number, NORAD ID, USSPACECOM object number or simply catalog number, among similar variants) is a sequential nine-digit number assigned by the United States Space Command (USSPACECOM) in the order of launch or discovery to all artificial objects in the orbits of Earth and those that left Earth's orbit. The first catalogued object, catalog number 1, is the Sputnik 1 launch vehicle, with the Sputnik 1 satellite having been assigned catalog number 2.

Objects that fail to orbit or orbit for a short time are not catalogued. The minimum object size in the catalog is 10 centimetres (3.9 in) in diameter. As of October 21, 2023^[update], the catalog listed 58,010 objects, including 16,645 satellites that had been launched into orbit since 1957 of which 8,936 were still active. 25,717 of the objects were well tracked while 2,055 were lost. In addition USSPACECOM was also tracking 16,600 analyst objects. Analyst objects are variably tracked and in constant flux, so their catalog and element set data are not published. As of September 12, 2023^[update] ESA estimated there were about 36,500 pieces of orbiting debris that are large enough for USSPACECOM to track.

Permanently catalogued objects are assigned a number from 1 to 69,999 or above 99,999. Space-Track is expected to start publishing objects greater than 99,999 in 2020 starting with debris discovered by Space Fence.

Space Command shares the catalog via space-track.org, which is maintained by the 18th Space Defense Squadron (18 SDS).