Nuclear-powered submarines generate large amounts of heat that must be dissipated into the surrounding ocean using a heat exchanger for reactor cooling. Diesel-electric submarines dissipate detectable heat when near the surface charging their batteries. This proposal primarily addresses the detection of nuclear-powered submarines but conventional diesel vessels can be detected near the surface. Although the ocean is a near-infinite heat sink, some small temperature change, detectable by a modern sensitive radiometer, will be observable at the sea surface from an airborne platform. Modern radiometers can detect surface temperature changes of fractions of a degree kelvin. Temperature changes due to a potential target will be discriminated from random surface fluctuations by recognizing a regular linear or near-linear pattern due to submarine motion. In Phase I, the temperature change at the surface will be estimated by using fluid dynamics and heat transfer calculations. Since many system parameters depend on radiometer operation frequency, a preliminary design will be formulated based on airborne platform constraints, area coverage, data refresh time, and other relevant parameters. During the Phase I Option, measurements of water temperature change due to subsurface heating will be made with a commercial infrared heat sensor under a variety of relevant conditions. For Phase II, a laboratory radiometer will be fabricated and tested under realistic conditions. For commercialization, companies involved with oil field development and hazardous waste mitigation as well as atmospheric sensing will be involved. A military application would use an airborne or ground-based radiometer that would be useful to detect engine heat from tanks, jeeps and trucks as well as body heat from humans even when obscured by smoke, fog, and radar-spoofing chaff. This detection capability would be useful in Army, Air Force, and Marine tactical operations. Although thermal infrared imagers can detect vehicles and humans, they do not have the ability to penetrate battlefield obscurants.
