The enemy from within: a Hill Air Force Base, Utah, unit keeps an aye on the sky, making it virtually impossible for aircraft to fly undetected over the United States

Airman, Dec, 2003 by Orville F. Desjarlais, Jr.

While smoke still billowed from the World Trade Center and the Pentagon after the Sept. 11, 2001, terrorist attacks, Pentagon officials turned to the 84th Radar Evaluation Squadron to learn exactly what happened.

Within two hours, the unit from Hill Air Force Base, Utah, had reviewed the radar trails of the four aircraft commandeered by terrorists. Using software the unit developed, evaluators created what's called a track of interest analysis on each hijacked civilian aircraft. Their software eliminated the clutter of all other traffic flying above the United States that fateful day. Imagine looking at the blips on the monitor of an air traffic controller in Las Angeles, multiplying those radar blips by 100--then zooming in on the flight path of a single aircraft. Nobody else in the Department of Defense has that capability.

The good news was the Hill unit captured most of the flights of all foul" aircraft and sent that information up the chain of command. The bad news was they had lost sight of United Airlines Flight 93 that crashed in western Pennsylvania, amplifying a defense weakness: America's heartland was exposed to danger. When the hijackers switched off the aircraft transponders--a radio signal that allows air traffic controllers to track each aircraft--the civilian airliners were virtually "invisible" to the Federal Aviation Administration.

"We could show the hijackers when they were near the eastern coast, but the hijacked planes went so far interior that we lost sight of them," said Master Sgt. Rob Freedman, a squadron superintendent.

Before Sept. 11, the unit focused attention on radars located around the nation's borders. Like wagons in a circle, these fully functional sites were used to protect America from outside threats. There were many more radar sites in the country's interior, but they were only being partially used by the FAA to track commercial aircraft that used transponders. After 9/11, that all changed.

"Our aerospace control and air defense missions have traditionally been oriented to detect and identify all aircraft entering North American airspace, and, if necessary, intercept potentially threatening inbound air traffic" said Gen. Ralph Eberhart, commander of the North American Aerospace Defense Command and the U.S. Northern Command. He's also the 84th's main customer. "We are now also focused on threats originating within domestic airspace, such as hijacked aircraft," Eberhart added.

Immediately after the attack, the 84th was determined to come up with a plan to help keep Americans safe. The unit's idea was to optimize all the radar sites so the Air Force and FAA could work hand in hand in securing the skies.

There are two radars at every site. The FAA primarily uses beacon radar, which captures aircraft transponder signals. The other radar, known as search radar--the one the Air Force is interested in using--transmits 4,000,00 watts of power to beam signals 200 miles in all directions. It reflects and captures radar signals off aircraft, Before Sept. 11, search radars weren't used at sites in America's interior. The Air Force is now interested in using this capability at all sites. If an aircraft's beacon is turned off, the Air Force can now use search radars to still keep tabs on it.

However, these search radars are pointed too high to track low-flying aircraft. It's like putting up an electric fence that's high enough to keep cows from wandering around, but not low enough to keep the wolves out. The idea is to keep the wolves at bay, so the radar unit is sending teams of engineers, radar maintainers and civil engineers across America to make adjustments.

"FAA radar is tilted up," said Staff Sgt. John Dixon, an 84th radar sensor evaluator. "We go in and jack it down. We also evaluate their systems to find ways to make them better."

This means not only ensuring the FANs 50-yearold equipment is working properly, but also that after analysis and adjustments, the equipment's performance improves by 10 to 20 percent. The team expects to have all the sites operational by 2006.

The team also makes sure each radar site has a recorder. It's like hooking up a video cassette recorder to each system. This will give the squadron the capability to record and play back radar data from any of the interior sites and remotely monitor each radar's performance. The data identifies not only the specific aircraft involved, but also its altitude and location at any given moment.

"We check out every little detail, from antenna to transmitters and receivers," said Darrell McFarland, the unit's technical advisor and a team chief. "We balance FAA and Air Force needs."

The radar sites are scattered across America, and they're located at time highest points in the regions, usually atop remote mountains. Optimizing all the radar sites means a lot of temporary duty.

Tech. Sgt. Lanis Williams, a radar system evaluator, spends about 180 days a year on such trips.

"What we do is unique," Williams said. "It's challenging to work on radars that were made in the 1950s. It's also good to he on a team that helps America have a good defensive system. We don't want to digress into pre-9/11."