Abstract: A side-looking sonar is provided with the wide angle acceptance characterics of a wide receiving beam together with the high resolution of a narrow receiving beam, while retaining both echo and shadow detection capability, through the use of a plurality of transducers disposed at such angles that their respective narrow beams cross one another at a location between the transducers and the ranges of interest and the distal portions of the beams lie adjacent one another. Individual returns received from the beams as the sonar is moved along a path normal thereto are coherently combined and detected.

Abstract: A dual frequency, synthetic aperture, sonar system includes a transmitter r projecting insonifying pings alternatively at first and second frequencies and a linear receiving array carried by a vehicle so as to receive returns from said pings. The first and second frequency returns are separated and subjected to processing in parallel channels where they are resolved into in-phase and quadrature components for subsequent phase-error correction, coherent addition, and synthetic aperture beamforming.

Abstract: An apparatus and method for detecting the presence of, and severing command ables submerged in an aqueous medium, utilizing a galvanic current pulse generated by a galvanic cell with one electrode thereof serving as a cable cutter.