Single element synthetic aperture using an ocean glider

Abstract

The feasibility of using a single transducer element on an ocean glider to create a synthetic aperture is discussed. Acoustic data were collected on two Webb Slocum gliders deployed by Rutgers University during the Shallow Water Experiment (SW06) on the continental shelf off New Jersey. These gliders periodically surfaced for GPS fixes and data transfer via satellite phone. A synthetic aperture is created through coherent processing of the acoustic data as the glider travels through the water. A number of issues including changes in depth, nonsteady motion of the glider, and clock drift can limit the performance of the processing. However, the glider provides a low‐noise and low‐speed platform, potentially improving the signal‐to‐noise ratio. The geometry of the experiment provided for near‐broadside recording of the 224‐ and 400‐Hz WHOI tomography sources. An acoustic normal mode representation of the field provides the basis for processing of the data similar to the Hankel transform approach of Frisk and Lynch [J. Acoust. Soc. Am. 76, 205–216 (1984)] and Holmes et al. [J. Acoust. Soc. Am. 119, 3346 (2006)]. Effects of spatial variations in sound speed are examined. [Work sponsored by the Office of Naval Research.]