The USAF set up a sizable UFO detection network in the 1980s, called GEODSS, the Ground-based_Electro-Optical_Deep_Space_Surveillance System. It's a set of pairs of large (40-inch) computerized telescopes which watch the sky automatically. The system has a star catalog and knows what should normally be visible. This includes noticing dark objects which occlude stars. It was intended to look for USSR satellites and space debris, but it can detect just about anything in near-Earth space. There are three active installations of this system. Most near-earth asteroid detections come from a former GEODSS station now operated by MIT's Lincoln Labs.

Unlike most astronomical telescopes, the GEODSS stations have a pair of telescopes some distance apart, under common control. They can range near-earth objects by parallax. One of the less-publicized features of the system is that one of the telescopes has a laser, so dark targets can be illuminated.

(In my aerospace days, the specs for this system crossed my desk. Our company had bid on the system, but lost.)

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