The AN/MPQ-64 Sentinel is an X-band electronically steered pulse-Doppler 3D radar system used to alert and cue Short Range Air Defense (SHORAD) weapons to the locations of hostile targets approaching their front line forces. It is currently produced by Raytheon Missiles & Defense. First built in 1997 as a modification of AN/TPQ-36A for search and track role in the Norwegian NASAMS air defense system, the Sentinel radar is deployed with forward area air defense units of the U.S. Army. Mounted on a towed platform, it can be positioned remotely from the rest of the unit. Main characteristics The antenna uses phase-frequency electronic scanning technology, forming sharp 3D pencil beams covering large surveillance and track volume. It uses a rotating platform with a high scan rate (30 RPM) to provide 360 degree coverage. The radar is designed with high resistance to electronic countermeasures (ECM) and anti-radiation missiles (ARM). The system automatically acquires, tracks, classifies, identifies and reports high- and low-altitude targets, including cruise missiles, unmanned aerial vehicles, and both rotary- and fixed-wing aircraft. Identification of friendly aircraft is aided by identification friend or foe (IFF) interrogation. The system can be deployed using HMMWV fitted with a 10 kW 400 Hz 115/200 VDC on-board power generator. It can be operated autonomously and communicate with the fire direction center via wideband fiber-optic link. It can also distribute its data over a SINCGARS radio network. AN/MPQ-64A1 Improved Sentinel Under A1 Improved Sentinel modernization program, existing Sentinel units are equipped with modern digital COTS-based electronics for signal and data processing, which ensures greater performance and allows software modification for quick updates of fielded systems. Waveform upgrades for the receiver/exciter and the replacement of the transmitter with power amplifier modules allows Sentinel to generate, receive and filter low-intensity target classification waveforms. Variable rotation rate increases time on target and position the antenna to improve classification and tracking of smaller cruise missile targets. Updated software supports classification of beyond visual range targets and electronic countermeasures. The upgrade provides a significant range extension and better detection against subsonic cruise missiles, slow-moving Unmanned Aerial Vehicles and drones, and rotary-wing and fixed-wing aircraft. AN/MPQ-64F1 Updated version of Improved Sentinel for the NASAMS 2 air defense system. AN/MPQ-64M2 Employed by the Dutch Joint Ground-based Air Defence Command. AN/MPQ-64A3 Enhanced Sentinel The U.S. Army ordered the A3 Enhanced Sentinel improvement program in 2011. The upgrade includes the TPX-57 Mode 5 Identification Friend