The Feltwell balls were originally the visible face of the US Air Force’s 5th Space Surveillance Squadron (5 SPSS)

It was part of the USAF’s Passive Space Surveillance Network which tracked the physical location of emitting satellites in orbit. This data along with that from other systems was used to adjust the orbits of various satellites and manned vessels (for instance the Space Shuttle and the International Space Station) to reduce the risk of on-orbit collisions.

This unit moved out of Feltwell in 2003.

So it would be believed that they are currently not active, but then this could always be a double-bluff, much as for the fact that security on the base has been greatly relaxed since that time.

Moggy