The 1960s era HARM (High-speed Anti-Radiation Missile) has received a
major upgrade, and is now being called "HDAM" (HARM Destruction of
enemy air defense Attack Module). The original HARM was a missile guided by
signals being put out by enemy radars. HDAM overcomes a common trick radar
operators used to protect themselves, by turning the radar off. HARM got around
that by homing in on the last location of a transmission. HDAM goes one step
further, and uses GPS (with inertial guidance as a backup) to take the missile
to where some over system (satellite, aircraft or UAV) had located a radar.
Tests have demonstrated that HDAM is accurate enough to destroy radars this
way. HDAM can still find radars the old fashioned way, if the radar is turned
on. More importantly, the HDAM can be fired far enough away from a radar, that
the anti-aircraft missiles the radar is spotting for, are less of a risk.
the United States produced the first HARM missiles, several other nations now
make them as well.