Periscope Test Facility
Building 94
An industrial-looking building with few windows stood on this site directly in front of the fort from the 1770s until 1999. It was designed specifically for top-secret work in periscope technology.
Originally, periscopes were simple tube-shaped optical devices that permitted a submarine crew to see above the surface when the ship was underwater. The research that took place in this building was instrumental in developing increasingly sophisticated types of periscopes, incorporating cameras and high-tech antennas.
The navy expanded a former machine shop in 1977 and added a tall tower to form this building. Nine years later, the navy enlarged the tower and added a second floor. The seventy-five-foot-high tower had room to test six periscopes in a fully extended, vertical position. Researchers could raise three periscopes to project above the building through trap doors in the tower roof. In this position the periscopes could transmit and receive communications from satellites, as well as receive radio, radar, and optical signals from various other sources.
Marker can be reached from East Street, on the left when traveling south.
Courtesy hmdb.org
