Satellite Catalog Number
The Satellite Catalog Number (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 centimeters in diameter. As of June 11, 2021[update], the catalog lists 48,833 objects, including 11,264 satellites that have been launched into orbit after 1957. 21,197 of the objects were actively tracked while 1,374 were lost. ESA estimates there are about 34,000 pieces of orbiting debris that are large enough for USSTRATCOM to track as of January 2019.
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.