SSQ-57

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Developed by the United States Navy and used by a number of allies, AN/SSQ-57 sonobuoys are passive acoustic, low-frequency listening devices dropped from aircraft and helicopters. In antisubmarine warfare, they help localize submarines detected by long-range sensors or other devices. Because they are passive, they give off no noise to alert the target.

The AN/SSQ-57B is the currently issued model of calibrated low-frequency analysis and recording (LOFAR) sonobuoy. It is a low-frequency version of the earlier AN/SSQ-41 passive sonobuoy, no longer in service. Once dropped, it can operate for a preset one, three, or eight hours. It can deploy its microphone at a depth of 90 or 400 feet. It can transmit data back on 31, or, with an upgrade, 99 radio channels.

A variant, the AN/SSQ-57M, is moored on the bottom rather than dropping its microphone from the water surface. Both are standardized "A" size devices (36 inches long 4 7/8 inches in diameter), which can be mixed with other sonobuoy types in the same dispenser.