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his article discusses a new idea called cognitive radar. Three ingredients are basic to the constitution of cognitive radar: 1) intelligent signal processing, which builds on learning through interactions of the radar with the surrounding environment; 2) feedback from the receiver to the transmitter, which is a facili-tator of intelligence; and 3) preservation of the information con-tent of radar returns, which is realized by the Bayesian approach to target detection through tracking. All three of these ingredi-ents feature in the echo-location system of a bat, which may be viewed as a physical realization (albeit in neurobiological terms) of cognitive radar. Radar is a remote-sensing system that is widely used for sur-veillance, tracking, and imaging applications, for both civilian and military needs. In this article, we focus on future possibilities of radar with particular emphasis on the issue of cognition. As an illustrative case study along the way, we consider the problem of radar surveillance applied to an ocean environment. According to the Oxford English Dictionary, cognition is “knowing, perceiving, or conceiving as an act. ” Given three dis-tinct capabilities: ■ the inherent ability of radar to sense its environment on a continuous basis ■ the ability of phased-array antennas to electronically scan the environment in a fast manner ■ the ever-increasing power of computers to digitally process signals it is our conviction that it is indeed feasible to build a cogni-tive radar system using today’s technology. Indeed, if ever there was a remote-sensing system well suited for cognition, radar is it. From the moment a surveillance radar system is switched on, the system becomes electromagnetically linked to its surround-ing environment in the sense that the environment has a strong and continuous influence on the radar returns (i.e., echoes). In so doing, the radar builds up its knowledge of the environmen