Reconnaissance sonar for deep ocean seamount detection

A system design concept for deep ocean seamount detection at athwartship ranges to 16 km is presented. The calculation of required sonar parameters is based on actual measurement of seamount backscatter levels, employing a non-linear acoustics source wlth similar beamwidth and frequency. Shadow zones limit the system´s ability to distinguish between seamounts and abyssal hills. Consequently the maximum range is a function of refraction, minimum depth statistics, elevation angle measurement accuracy, and permissible false alarm rate. The physical size and basic sonar parameters of the new AN/SQS-56 sonar are compatible with the requirements for a reconnaissance sonar. In addition the sector scan indicator can measure arrival angles to better than 1/5 of the 10° beamwidth. Major required modifications include a 90° axial rotation of the 7.5 kHz array and addition of a refraction corrected display.