AN/SPG-51

The AN/SPG-51 is a tracking / illumination radar for RIM-66 Standard missiles. It is used for target tracking and Surface-to-air missile guidance on Virginia-class cruisers, California-class cruisers, and Kidd-class destroyers.

The French Cassard class frigates and Royal Netherlands Navy Tromp class frigates also utilise this system.

Older variants were used on Charles F. Adams-class destroyers.

Aircraft tracking is based on monopulse radar utilizing Pulse-Doppler radar signal processing in MK 74 MOD 14 and MK 74 MOD 15. The MK 74 MOD 15 configuration includes continuous-wave radar tracking in addition to pulse-Doppler tracking. It provides illumination for bistatic radar operation associated with missile guidance in all configurations. Older systems rely on conical scanning rather than monopulse.