Underwater vehicles equipped with laser beacons and tracked from aircraft.

The successful results of a feasibility experiment for tracking underwater vehicles equipped with laser beacons by aircraft equipped with detectors are presented. The system design focuses on tracking limited payload vehicles such as torpedoes in shallow-water (0-200 m) environments during Navy test and evaluation exercises. A compact, battery operated, Q-switched, frequency-doubled, dual-pulse Nd:YAG laser operating at 532 nm was used. The upward-pointing laser with a diffuse 14° output beam was mounted to a stationary buoy at a depth of five attenuation lengths. Aboard an SH3 helicopter at 5000 ft (1524 m), a 14° field-of-view avalanche photodiode detector system detected the first pulse that triggered an image-intensified CCD camera to image the second pulse at the ocean surface. When the results were scaled, we concluded that a coverage diameter of 14,375 m could be achieved at an aircraft elevation of 1 mile (1.6 km) with a signal-to-noise ratio of 10:1 for depths of ten attenuation lengths.