This paper describes an advanced sonar system designed specifically for ocean bottom search and survey applications within the depth limits of the continental shelf.
BO'SUN is a 36 kilohertz system which employs multiple adjacent 50 beams (11 or 21, optional) arranged to simultaneously take multiple sonar samples of the ocean bottom along a line perpendicular to the ship's axis. The processed echo signals from the multiple beams are displayed on a cathode ray tube to provide a real time display of the cross track profile along the Ship's track.
In addition, a stabilized vertical beam is also provided. The beam which is nearest to the true vertical at any instant of time is electronically switched to an output line for recording. This output is compatible with most any of the popular graphic recorders.
An analog to digital signal processing subsystem is available for digitizing the ship's attitude information and the sonar range data from each of the multiple beams for direct input to a digital computer or data logger. The digitized sonar data together with appropriate navigation data can be further processed by a general purpose computer in real time, or off-line, for the purpose of contour chart generation.
The BO'SUN is based on concepts developed during the design of two General Instrument multi-beam sonar systems. These systems were designed and built for use on U. S. Navy and U. S. Coast & Geodetic Survey oceanographic ships. Specifically, these systems are the Sonar Array Sounding System (SASS) and the Narrow Beam Echo Sounder (NBES). The SASS system operates at 12 KHz, is electronically stabilized and employs extremely narrow beams which are capable of obtaining 61 soundings per transmission. The SASS sonar data is processed in real time for the purpose of generating contour charts. The NBES is a 12 KHz system which also employs electronic stabilization. The NBES has fifteen, 2-2/3° beams and is capable of sounding at depths in excess of 4,000 fathoms.
Approximately 20 months ago, a prototype of the BO'SUN system was constructed. This multi-beam sonar was based on the concept of the deep water systems discussed above, but designed specifically for continental shelf use. Our design goal was to build a much less expensive system, but one which would provide maximum utility for search and survey and which could be mounted on a small workboat and still be capable of sounding to depths of 2,000 feet. The beam dimensions and operating frequency were selected to provide reasonably high resolution and reliable sounding capability to 2,000 feet.
A photograph of the BO'SUN electronic console and the 11 beam transducer array is shown in Fig. 1. The 21 beam transducer array is shown in Fig. 2.