The spy next door: What went on in Russia's shuttered U.S. compounds?

Desmond Ball, the centre’s late director, wrote of Pioneer Point, “the complex is extremely well-placed for SIGINT (signals intelligence) operations.”

He explained that the location was in the main microwave communications corridor between Washington and the massive U.S. Naval base — the world’s biggest — in Norfolk, Virginia. Ball also noted that “NSA headquarters at Fort Meade is 35 miles directly west; the large Navy communications station at Annapolis (used to communicate with nuclear submarines) is 20 miles west southwest; and the NSA’s Propagation and Research Laboratory on Kent Island is 15 miles to the southwest.”

Officials say the Soviets and their Russian successors were brazen about the facility’s mission. Starting in the late 1970s, antennas went up on the main building. Soon, the mansion and surrounding property was festooned with all manner of antenna for capturing communications and other signals.

The Reagan administration began a major communications effort to secure the links and also cut down on the Soviets’ access to U.S. communications technologies, thwarting plans to install a large satellite dish at Pioneer Point.