The AGM-122 Sidearm is a small Anti Radiation Missile, carried on the Army AH 64A/D Apache and Marine Corps AH-1W SuperCobra attack helicopters for self defense against anti aircraft gun and SAM radars.
The AGM-122A is a rebuilt AIM-9C Sidewinder, a semi-active radar homing missile using a conically scanning semi-active seeker. Originally designed for the F-8 Crusader, it was unique among the Sidewinder variants, which are all otherwise infra-red guided. In the mid-1980s several hundred of these missiles were refurbished and redesignated as the AGM-122A Sidearm in response to a Marine Corpsrequirement for a lightweight Anti-Radiation Missile to arm Marine Corps AV-8s, A-4s and helicopters.
Modifications developed at the China Lake Naval Weapons Center and produced by Motorola included improved semi-active seeker electronics to provide coverage of the greater bandwidth required to home in on a range of air defense radars. The AIM-9C's original Mk.17 motor and WDU-17 warhead were retained, with the substitution of a DSU-15 active fuse. Control electronics were modified to command an immediate pop-up after low-level launch to provide a dive attack on the target radar.

Although the resulting capability was vulnerable to countermeasures and rather limited compared to more robust anti-radar missiles such as HARM , it does provide a useful self-defense capability against low-level anti-helicopter threats such as the ZSU-23 or SA-8.