Partial synthetic aperture beamformer

Synthetic Aperture Sonar (SAS) was developed as a means to produce long apertures that can create images at high resolution, usually achieved by collecting data on a platform with a predictable trajectory However, Autonomous Underwater Vehicle (AUV) technology has matured and now includes operational conditions where system trajectory is not predictable (e.g. autonomous redirection behavior). Partial aperture SAS (PSAS) can be used to provide image data for autonomous behaviors with relatively low data latency and can be used to minimize the effects of non-linear trajectories on SAS image production by providing imagery with minimal latency, but at lower resolution compared to full aperture imagery. This paper explores a technique that uses a range invariant aperture to form SAS images to provide the highest achievable resolution given a specified maximum aperture length (or data latency). A simulation is used to measure the effect of the range-invariant aperture on resolution and results are compared with theoretical values. PSAS techniques are also used to produce imagery from an existing SAS system, and imagery produced at various aperture lengths is compared. Results show that the effects of PSAS on image quality and resolution are predictable. Therefore, future efforts to develop image queued autonomous behaviors can trade data latency and image resolution to optimize system performance.