What type of guidance does the AGM-88 HARM utilize?

The AGM-88 High-speed Anti-Radiation Missile (HARM) primarily uses passive radar guidance. This means it is designed to detect and home in on the radar emissions from enemy radar systems. By identifying the signals emitted by these systems, the missile can determine its target accurately without the use of its own active radar, which helps to avoid detection and enhance its stealth capabilities.

Passive radar guidance is particularly effective for anti-radiation missions as it allows the missile to be fired at targets that may be operating their radar systems, yet it remains undetected until it's too late for the enemy to respond. This characteristic is essential for suppressing enemy air defenses and provides a tactical advantage in engaging radar-equipped threats.

Other guidance methods, like active radar or GPS, are designed for different types of engagement scenarios, focusing on different target types or utilizing different detection ranges, which do not align with the specific operational purpose of the HARM.