The Mobile Detection Assessment and Response System, Exterior (MDARS-E) provides an automated robotic security capability for storage yards, petroleum tank farms, rail yards, and arsenals. The system includes multiple supervised-autonomous platforms equipped with intrusion detection, barrier assessment, and inventory assessment subsystems commanded from an integrated control station.The MDARS-E Intrusion Detection System consists of a motion sensor suite which is selectively enabled while the vehicle is momentarily halted in execution of pre-defined but randomly executed patrols. The system can detect a crawling, walking, or running intruder at a distance of 100 meters, even in darkness or the presence of smoke, fog, dust, and precipitation. The demanding nature of the required detection criteria necessitates the integration of complementary technologies which can sense motion, pattern characteristics, thermal signatures, and temporal behavior.Accordingly, MDARS-E incorporates a two-layered sensor approach (i.e., vision and radar) to achieve a high probability of detection while simultaneously minimizing the number of nuisance alarms. The primary layer utilizes an infrared/vision-based (FLIR) system, which provides high angular resolution of a suspected intruder location within a scene. This information is used to slave a two-axis pan-and-tilt turret on which both the radar and vision sensors are mounted to automatically track the designated target. The second layer, a long-range broad-area radar sensor, is thus optimally positioned to confirm the presence of any valid moving target, effectively eliminating nuisance alarms. This paper discusses the MDARS-E Intrusion Detection System sensors and user interface, with particular emphasis placed on the pulsed-Doppler radar implementation and performance.