Tuesday, February 24, 2015

New anti-sub sonar system engineered for small ships

By Richard Scott/IHS Jane's 360
23 February 2015
Thales has revealed details of a new anti-submarine warfare (ASW) sonar pairing specifically designed for small ship applications. Engineered to allow installation on offshore patrol vessels (OPVs) down to about 800 tonnes, the new CAPTAS-1 low-frequency variable-depth sonar and BlueWatcher hull-mounted sonar are intended to provide littoral navies with a credible ASW deterrent capability.
The CAPTAS family of low-frequency active/passive sonars was originally brought to market in the mid-1990s to meet growing demand for an improved surface ship ASW capability against quiet submarine threats. CAPTAS-1 builds on this pedigree, but shrinks the size to allow installation on small ships.
CAPTAS-1 uses a single - dependent tow for the active sonar source (a single free-flooded ring transducer operating at a centre frequency of about 1.5kHz) and a triplet receive array. Thales has also developed a compact and lightweight towed array handling system that uses a single automatic winch.
In July 2013, Thales (Stand B-030) conducted at-sea trials of a CAPTAS-1 engineering development model. According to figures released by the company, CAPTAS-1 will be able to operate at speeds of up to 12kts, and at depths down to 100m. Typical detection range is claimed to be in the region of 20-30km, depending on the target type and environmental conditions.
To enable installation on smaller OPVs, Thales has reduced deck footprint to 15m2 and weight to about 8 tonnes. One option is to install CAPTAS-1 in containerised form, with the sonar body/receive array and electrically powered towed array handling system housed in a standard 20ft shipping container; the winch control and electronic cabinets are installed in a 10ft container mounted adjacent.
Alongside CAPTAS-1, Thales is also introducing the BlueWatcher hull-mounted sonar, which repackages the transmitter and receive arrays from the FLASH airborne active dipping sonar to provide small ships with a compact, 360° multi-purpose sonar. Thales has engineered the BlueWatcher ‘wet end’ to fit in a cylindrical volume just 700mm in diameter and 600mm in height, limiting dome/draft requirements to 0.85m. Inboard components are limited to a single cabinet and the operator console.
Only a single hull penetration is required out to the array.
In active mode, used for ASW or collision/obstacle avoidance, BlueWatcher transmits on any one of three frequencies between 3-5kHz in FM (frequency modulation), CW (continuous wave) and combination pulse modes. In passive mode, the system can be used to detect small, fast surface craft. According to Thales, the implementation of adaptive beam-forming has delivered performance that is equivalent to an array twice the size. It also allows for installation on ‘noisy’ ships where there is no quietening or noise hygiene.

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