This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.
This is a distinct incremental value is a assigned to each new orbital object. Officially, it is known as the “Satellite Catalog Number”. NORAD started the counting at 1 and USSPACECOM who are now in charge of the numbering, have continued it.
The number is only used once, even if a satellite decays (re-enters the atmosphere).
This value can be up to 5 characters in length. As of recent, the number is up to 34540.
25544 - International Space Station 20580 - Hubble Space Telescope 00001 - Sputnik 1 Launch Vehicle (decayed)