Satellite catalog

The Satellite Catalog Number (also known as NORAD Catalog Number, NASA catalog number, USSPACECOM object number or simply Catalog number and similar variants) is a sequential 5-digit number assigned by United States Space Command to all Earth orbiting satellites in order of identification. Before USSPACECOM, the catalog was maintained by NORAD. The first catalogued object, catalog number 00001, is the final stage of the rocket which launched Sputnik 1. As of 22 September 2016, the NSSDC Master Catalog listed more than 40,000 tracked objects including 7,576 satellites launched into orbit since 1957.

...
Wikipedia