A free-floating, steerable, HF sonar for environmental measurements

Defence Research Establishment Atlantic is developing a free-floating HF sonar for collecting environmental acoustic data in the open ocean. The sonar is designed to operate in the band 20-40 kHz with a beamwidth of 0.1 steradians. Its maximum operating depth is 300 m. A 462 MHz RF command link is used to steer the array to any combination of azimuth and tilt angle. This facilitates measurements of directional ambient noise as well as surface and bottom backscatter as a function of grazing angle. Along with control over azimuth and tilt angle, the sonar is instrumented to monitor depth, roll and vertical acceleration. Data transmission back to the ship is accomplished via a 2.37 GHz RF data link capable of a data transfer rate of up to 8 Mbits/sec. In this paper, the electrical, mechanical, and acoustic design of the array is presented