Development and Performance of the AN/AAR-23(XB-1) Airborne Passive Submarine-Detection System

The AN/AAR-23(XB-1) equipment, an airborne passive detection system for use in airships, is designed to detect the surface scars from completely submerged submarines. This system, developed by NRL, is sensitive to 8-to-13-micron radiation and can passively detect changes in the radiation from the surface of the sea of less than ten parts per million. Tests conducted by NRL showed that this equipment can detect, at night, the scars from submarines operating down to keel depths of 400 ft in sea states up to 5 or 6 for periods up to three hours after the passage of the submarine. Subsequent improvement in detector-element performance should permit this capability from high-speed, fixed-wing aircraft.