(Over-The-Horizon, Backscatter) Designed and built by GE Aerospace, the OTH-B radar was deployed on the east and west coasts in the 1980s. The system reflected the radar beam off the ionosphere to detect objects from ranges of 500 to nearly 2,000 miles. The transmitter arrays operated at frequencies between 5 and 28 MHz. Fixed transmitter and receiving antenna arrays were separated by a distance of 80 to 120 miles.
This program has now been cancelled. The east coast transmitter site was located at Moscow AFS, ME, with a receiver at Columbia AFS, ME. The west coast transmitter site was at Christmas Valley, OR with the receiver at Tule Lake, CA, near Alturas. A third site was begun north of Gakona, AK, but was not completed.