The AN/MPQ-64 Sentinel is a three-dimensional radar used to alert and queue Short Range Air Defense (SHORAD) weapons to the locations of hostile targets approaching their front line forces. The Sentinel radar is deployed with forward area air defense units of the U.S. Army and USMC. The radar uses an X-band range-gated, pulse-doppler system. The antenna uses phase-frequency electronic scanning technology, forming sharp 3D pencil beams covering large surveillance and track volume. The radar automatically acquires, tracks, classifies, identifies and reports targets, including cruise missiles, unmanned aerial vehicles, rotary and fixed-wing aircraft. It uses a high scan rate (30 RPM) and operates at a range of 40 km. The radar is designed with high resistance to electronic countermeasures (EC