Mon, Jan 30, 2012 - Page 3 News List

Navy to acquire ‘listening sticks’

By J. Michael Cole  /  Staff Reporter

The Taiwanese Navy is purchasing hundreds of specialized sonobuoys from the US to augment its anti-submarine warfare capabilities, a US Department of Defense notice said on Friday.

Under the Foreign Military Sale, Taiwan will acquire 440 AN/SSQ-53F sonobuoys for US$335,000, with work scheduled for completion by January 2014 (as part of the same deal, the US Navy is purchasing 49,900).

Sonobuoys, also known as “listening sticks,” are used to detect and identify moving underwater objects.

The AN/SSQ-53F directional frequency and ranging (DIFAR) sonobuoy — the latest-generation passive sonobuoy used by the US Navy — is dropped from fixed-wing aircraft or helicopters and uses four hydrophones that operate at depths of 27m, 60m, 120m and 300m, as well as digital sound processors, to listen for enemy submarines.

Unlike “active” sonobuoys, which locate objects by bouncing a “ping” off a vessel, passive types gather emissions created by moving underwater objects.

Aircraft can drop a pattern of sonobuoys, which relay information back to the aircraft by radio link to determine the exact location of enemy submarines.

In Taiwan’s case, the sonobuoys are likely to be used on the 12 refurbished P-3C “Orion” marine patrol aircraft it has purchased from the US, which are expected to start being delivered this year.

Sonobuoys are designed to determine the direction from which a signal originates. Through triangulation, a pattern of listening sticks can determine a target’s range, bearing and location.

The operational life of a sonobuoy can be set from 30 minutes to eight hours, whereupon the device automatically scuttles itself.

In November last year, Taiwan also ordered 44 AN/SSQ-36s — ocean thermometers used to establish what is known as the “temperature geography.” Water temperature, which affects sonar propagation and acoustic range prediction, tends to vary depending on depth.

Establishing temperatures before launching sonobuoys, such as the AN/SSQ-53F, can therefore ensure optimal performance.

China has at least 65 submarines in its navy’s undersea forces, with four nuclear-powered ballistic missile submarines (SSBN), at least five nuclear-powered attack submarines and 56 conventional submarines.

The Type 094 SSBN, which is equipped with the JL-2 nuclear missile and was launched in 2004, has been of particular concern to the international community.

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