Military test used HAARP and Cold Bay receivers to detect aircraft beyond the horizon

A military experiment used the University of Alaska Fairbanks' HAARP research transmitter near Gakona and a new receiver array in Cold Bay to detect aircraft over the Gulf of Alaska and Bering Sea, Alaskan Command said Monday.

The tests, flown Sept. 7-11, were the last in a three-year series looking for ways to spot aircraft beyond the reach of Alaska's long-range radar sites, according to the command's release. Some of those sites date to the 1950s, Alaska News reported in August.

HAARP, the High Frequency Active Auroral Research Program, is a former military site now run by UAF's Geophysical Institute to study the ionosphere, the electrically charged layer of the upper atmosphere that carries radio signals. High-frequency signals can bounce off that layer and come back down far past the horizon. The military calls detections made that way "skywave."

To check whether the system worked, military planes flew as targets with known positions: an E-3 Sentry from the 962nd Airborne Air Control Squadron, HC-130J Combat King IIs from the 211th Rescue Squadron and KC-135 Stratotankers from the 168th Air Refueling Wing.

Initial results showed "full skywave (beyond line of sight) detections of aircraft and correlation to truth flights," the release said, and the team met or exceeded its test objectives. Analysis is continuing.

"Understanding what this technology can do in the Arctic starts with collecting data under real operating conditions," said Dr. Carolyn Stwertka, Alaskan Command's chief scientist.

The release doesn't say how far away the aircraft were or whether any were beyond the reach of existing radar.

MITRE, a federally funded research nonprofit, built the Cold Bay array and designed the field experiment. U.S. Northern Command, the Air Force Research Laboratory and Defence Research and Development Canada also took part.