Before revision: The United States Space Surveillance Network which has detectors such as the Space Fence (replacing the now defunct Air Force Space Surveillance System) and Space Surveillance Telescope The Russian Main Control Centre of Outer Space with facilities such as Okno and Krona
After revision: The United States Space Surveillance Network which has detectors such as the Space Fence (replacing the now defunct Air Force Space Surveillance System) and Space Surveillance Telescope The Russian Centre for Outer Space Monitoringand Sazhen-S, used to analyse the orbital parameters of space craft. with facilities such as Okno and Krona