A Digital Thin Line Towed Array for Small Autonomous Underwater Platforms

Conventional towed arrays have been built with large diameters to allow separation of the boundary layer from the array elements so that the effect of turbulent flow has less impact on the signal to noise ratio performance of the array. These arrays, therefore, tend to be bulky and heavy. The successful development of AUV and USV required the focus of towed array development to much smaller diameter and light-weight arrays. The Acoustic Research Laboratory (ARL) of the Tropical Marine Science Institute, National University of Singapore, arising from a recent requirement, has developed a light weight digital thin line towed array (DTLTA) for underwater sensing applications. The 10 mm diameter and 12 m long array weighing not more than 2 kg (excluding the tow cable) is a promising sensor platform for use from small autonomous assets such as AUV and USV and is believed to be the smallest diameter digital towed array ever developed. The digital output enables easy interfacing of the array to any micro-controller or PC-based data acquisition platform. A set of diagnostic and beamforming software tools were developed along with the DTLTA to help test the array. These tools are based on conventional beamforming techniques and Ronald Wagstaff's towed array diagnostics. In this paper we are presenting the details of the design and construction of the array, special features of the software tools developed and results from a tow test conducted using an AUV platform in local waters. Limitations of the current design and future development plans to improve upon them will also be discussed.