Maintaining the Balance...

Surface to Air Missile technology is one of those areas where small shifts in tactical capability could have large strategic effects; if reliable, effective, difficult to counter surface to air missiles become cheap and available, the most common manner in which rich countries pound the bejeezus out of poor countries loses much of its attraction. This possibility is not lost on the USN or the USAF. David Hambling:

Soon after radar-guided anti-aircraft missiles became a threat, planners realized that the simplest way to stop them was to take out the radar. These radars make an easy target; in radio terms, they are equivalent to lighthouses, radiating brightly. So in 1958 the U.S. introduced the Shrike, an "Anti-Radiation Missile" that homed in on enemy radar and proved invaluable in the Vietnam War. The modern successor is the AGM-88 HARM High Speed Antiradiation missile, which has longer range and a speed of over mach 2. "No U.S. aircraft has ever been lost to surface-to-air missiles when HARM has been flying cover," Mike Vigue, HARM Growth Manager at Raytheon, told me.

The problem with this type of missile is that it relies on the enemy radar being turned on. Once they spot a missile barreling towards them, the operators can turn off the radar so it has nothing to home in on. So the mission is known as Suppression of Enemy Air Defence or SEAD: you're not likely to kill them, but you can force enemy radar to shut down, making the skies safe for friendly aircraft.

All that changes when you can fit HARM with a GPS module that allows it to accurately pinpoint the location of the radar emitter. The addition means that even if the radar turns off, the missile can still hit it precisely.

Raytheon's upgrade is called HDAM, for HARM Destruction of Enemy Air Defenses Attack Module. It's being built for the Air Force. And it incorporates both GPS and an inertial measurement unit with a fiber-optic gyro. Raytheon won’t say exactly how accurate it is, but unlike other anti-radiation missiles which rely on a shrapnel warhead, HDAM has achieved "metal on metal" hits on radar targets, both emitting and non-emitting.