Detect, Classify, and Geolocate with Acoustic Technologies

The science and engineering team that designed and built the Multi-Sensor Towbody (MuST) platform are now demonstrating its capabilities in performance tests for the Naval Facilities Engineering Systems Command and the Army Corps of Engineers. During 10 days of surveying near the Florida Keys this past spring, MuST, now designated Technology Readiness Level 7, searched for hazardous objects buried in seafloor sediments. Towed by R/V Pelican in a lawnmower pattern, MuST flew at controlled altitudes above the bottom to search for mine-like objects that may have been left behind on a mid-20th century training field and subsequently buried over the decades. 

To detect, classify, and geolocate buried and proud mine-like objects at performance levels and area coverage rates superior to other modalities, the APL-UW team conceived the MuST system as a combination of underwater acoustic sensing technologies and shipboard handling and data processing systems. A specialized, three-dimensional, sub-bottom profiler manufactured by EdgeTech and two high-frequency sonar systems were integrated by the APL-UW engineering team with the FOCUS-3 towbody produced by MacArtney Underwater Technology. Together, the sonars image the top 1–2 m of the sediment with a resolution of 10 cm³ and the sediment–water interface at sub-centimeter precision. A fiber optic, two-way communication cable connects the towbody to the data acquisition and vehicle control systems. This division of components minimizes the number and complexity of in-water, at-risk technologies and provides operators aboard with a real-time image map of the sediment volume during survey operations. 

MuST was shipped from APL-UW to Cocodrie, LA, and loaded on R/V Pelican before its two-day transit to the survey site. “This was the first time MuST was operated with a non-APL-UW vessel and crew,” says Senior Principal Scientist Kevin Williams, “and the first in a ‘live’ operational environment with significant ocean waves and currents.” The survey covered 9 km² of nearshore waters about 30 m deep. The site had been a mine sweeping training field and unfortunately there are no records of mine-like objects having been recovered. “This was truly a ‘live’ site in that nobody knows what's on the bottom or buried in the sediment,” adds Williams. The survey identified six buried, man-made objects including an anchor, shrimp trawling hardware, and cables. No mines were found.

Next up for MuST is another site survey off the island of Vieques, Puerto Rico in May 2026. This Superfund site was used for naval training for decades. Remediation of the area around Vieques is a precursor to opening the region to recreational activities. And in the longer term, the team's goal is to build more copies of MuST and train commercial surveyors to use them.