From Citizendium, the Citizens' Compendium
The AN-APS-145 is the latest generation of surveillance and tracking radar used aboard the E-2C+ Hawkeye, an airborne early warning (AEW) aircraft that is carrier-capable. Much as is the AN/APY-2 radar carried by the much larger E-3 Sentry aircraft, its antenna is mounted on stilts on top of the aircraft, and looks rather like a flying saucer gripping the airplane. It can track over 20,000 targets.
This version is mechanically scanned. It will be replaced, on the E-2D upgrade of the aircraft, with a AN/APY-9 radar. While this will be a phased-array radar, like the radars of the next generation beyond the E-3, it will be a "hybrid", using passive phased array technology, but still rotating. Its phased array capabilities will be used to steer the beam onto specific targets seen during a mechanical scan.