Multistatic Acoustic Submarine Detection
Air-dropped sonobuoys are one of the most powerful tools for hunting for submarines; ONR has been working on improving this long-serving technology.
Starting in the early 2000s, the Office of Naval Research has worked to develop multistatic active acoustic submarine detection systems. A multistatic system is characterized by one receiver receiving transmissions from more than one transmitter, and vice-versa. Acoustic systems in the ocean exhibit this behavior most effectively over the continental shelf, where sound waves can fill the water column through reflections from the bottom and surface. Modern multistatic transmitters use coherent waveforms rather than explosions.
A focus of the Cold War, antisubmarine warfare remains an important part of naval warfare. Finding newer, quieter submarines across the multitude of the world’s underwater environments is a challenging task.
(U.S. Navy photo by MC1 Ace Rheaume)
Work at ONR has focused on multistatic coherent active air-dropped sonobuoys operating over the continental shelf. Early work developed flex tensional transmitters that allowed performance criteria to be met in a smaller volume, in-buoy signal processing to aid in monitoring large sonobuoy fields, and cross-receiver contact fusion that allows operators to track submarines across a field of sonobuoys. Work in the late 2000s focused on placing a field of transmitters and receivers for best performance, predicting evolving field performance from in-situ environmental measurements, and tracking motion of sonobuoys after deployment. Environmental measurements and sonobuoy tracking are combined to predict when replenishment of the sonobuoy field is needed.
Current developments feature ping control algorithms to prevent mutual interference when one receiver is receiving transmissions from more than one transmitter, and improved batteries to enable transmitters to operate more rapidly or longer. Many of the ONR developments have transitioned to the Multi-static Active Capability (MAC) program of record, which started in the early 2000s soon after the ONR program began. In-buoy signal processing has not transitioned yet, although it is on the agenda for future builds of MAC.