> NORAD maintains general perturbation element sets on all resident space objects. These element sets are periodically refined so as to maintain a reasonable prediction capability on all space objects. In turn, these element sets are provided to users. The purpose of this report is to provide the user with a means of propagating these element sets in time to obtain a position and velocity of the space object. [1]

For the curious, here is the wikipedia page [2] with details on the US Space Surveillance Network used to obtain this data (30+ ground-based radars and optical telescopes worldwide, plus 6 satellites in orbit).

[1] https://www.celestrak.com/NORAD/elements/supplemental/ (didn't link directly to the starlink txt file on purpose, link for reference only, please don't hug the site to death)

[2] https://en.wikipedia.org/wiki/United_States_Space_Surveillan...