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Chelsea Technologies Group Ltd has extensive expertise in electronics and acoustics and can custom design and manufacture systems, or elements of systems.  To read about previous designs click on blue button below: 

Acoustic Telemetry SystemsAcoustic telemetry systems
Sonars for submarines & surface shipsSonars for submarines & surface ships
Warning Pingers, Towed Synchronised Pingers & Torpedo Recovery PingersWarning Pingers, Towed Synchronised Pingers & Torpedo Recovery Pingers
Arrays for Sidescan SonarsArrays for Sidescan Sonars
Spread Spectrum combined Acoustic Positioning & Communications (POSCOM)Spread Spectrum Combined Acoustic Positioning & Communications (POSCOM)

Other designs include:

  • Sea Shadow

  • Sonar Acoustic Source systems & Echo Repeater

  • Acoustic Transducers and Hydrophones

  • Digitally Multiplexed Towed Arrays and Seismic Streamers, Active Sonobuoys

  • Vertical Line Hydrophone and Source Arrays

Datasheet

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Acoustic Telemetry Systems

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The Chelsea Technologies Group offers a custom design and manufacture service for acoustic telemetry systems and acoustic modems. We have designed and manufactured custom telemetry systems and modems for both commercial and military customers.

Companies using the Chelsea systems include BAeSEMA and GEC-Marconi as part of their exercise mines, which are used for training mine hunting crews. These acoustic telemetry / modem systems are in-service with the United Kingdom, United States of America, Canadian, Australian and Belgian Navies. Chelsea Technologies Group telemetry systems have covered frequencies from 8kHz to 60kHz, and been used for applications such as data transfer and complex telemetry.

All these systems have optional GUI (Graphical User Interface) control systems running under Windows NT4 or 95/98, which have been developed to provide easy control of these advanced acoustic telemetry systems.

VEMS Excercise Mine System - courtesy BAeSEMA

Stonefish Excercise Mine System - courtesy GEC Marconi

VEMS telemetry electronics

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Sonars for Submarines & Surface Ships

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The Chelsea Technologies Group offers a custom design and manufacture service for sonar systems and sonar system components. Active sonar and passive sonar systems are supplied for both surface ships and submarines. These are produced to cover functions such as intercept, navigation, obstacle avoidance and high power tracking pinger output.

Sonar equipment designed and manufactured by the Chelsea Technologies Group Ltd is included in many UK submarines as the outboard components of Sonar 2077.  Chelsea also offers technical and logistics support to the UK MOD, DERA, etc. for both in-service and new-generation sonar systems.

Sonar 2077

Sonar 2077

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Towed Synchronised Pingers

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Towed Synchronised Pinger System
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Towed Synchronised 
Pinger System

Chelsea offers a custom design and manufacture service for acoustic synchronised pinger and triggered pinger systems.

Chelsea Technologies Group Ltd supply the STAB4 towed synchronised pinger system, which is used on the BUTEC underwater, tracking range in Scotland. This advanced pinger system, which was designed and developed for the UK DGUS, can be towed up to a speed of 25 knots and can be commanded using acoustic telemetry from a surface vessel.  
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 It is a fully synchronised system and achieves a timing accuracy of better than 200 microseconds over its 12-hour battery life. Chelsea Technologies Group Ltd also supply tracking pingers for use on the Rhona range in Scotland, this system mounts within the 'sea chest' of submarines. Torpedo recovery pingers have also been designed and manufactured for several different torpedoes.
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Chelsea Technologies Group Ltd also produces a PC-based portable synchronised pinger and receiver system, or Distance Measurement Equipment (DME), for use on submarines or surface ships. This slant range processor and synchronised pinger system can be interfaced with a vessel's sonar to provide a synchronised pinger or a synchronised receiver that can display slant range.  
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Remote DME system components

Slant Range Processor...

 

In DME (Distance Measuring Equipment) mode, VASS can transmit or receive underwater acoustic tracking pulses. This system is used to measure the slant range between the towed body of VASS and the vessel under test. So that the vessel under test can display the slant range a Remote DME unit is provided which has all the digital signal processing and synchronisation equipment mounted within a PC.  The configurable parameters are controlled via an easily operated Graphical User Interface, running under Microsoft Windows 95/98/NT4  
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  Specification 

Slant Range (DME) System:

Synchronised ranging system

Frequencies:

Selectable depending on the vessel's sonar

Synchronised:

Via VHF radio to vessel under test

Oscillator:

Highly stable oven controlled oscillator

Remote DME System:

For use in vessel under test

PC:

Small mains powered PC with LCD screen

Cards included in PC:

DME processor and DME DSP card

Printer:

Portable ink jet

Transmit Interface:

Underwater telephone system or 
separate transducer(s)

Receive Interface:

Analogue or digital feed from suitable vessel's 
sonar or separate transducer(s)

Synchronisation:

Interface to vessel's VHF radio set

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Arrays for Sidescan Sonars

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The Chelsea Technologies Group offers a custom design and manufacture service for sidescan sonar arrays and the electronic and processing systems associated with sidescan sonar arrays. We specialise in designing and producing state of the art sidescan sonar arrays and interferometers for integration into OEM systems.

The Deepscan 60kHz sidescan / interferometer, image courtesy of Ultra Electronics Ocean Systems.

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Sidescan sonar arrays from the simple to the very complex have been supplied to organizations such as Ultra Electronics, C-Max, Sonar Equipment Services and the UK Navy. Sidescan sonar array designs are available covering frequencies between 60kHz and 700kHz.

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Piezocomposite Sidescan Sonar Array

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1-3 Piezocomposites for imaging sonars - Picture courtesy of DERA Farnborough.

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We recently announced the availability of the first commercially priced piezocomposite high-resolution sidescan sonar array. Offering improved beam pattern stability and ultimately higher resolution than conventional monolithic sidescans, piezocomposites promise to revolutionise the sidescan manufacturing industry. The launching of piezocomposites for imaging sonar follows on from our recent development of high frequency piezocomposites in conjunction with the UK's Defence Evaluation and Research Agency (DERA).

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Other Arrays

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Chelsea Technologies Group, in addition to sidescan sonar arrays, can also design and manufacture acoustic arrays for other purposes such as detection or tracking.

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POSCOM is a spread spectrum underwater positioning system developed under the SeaSense program in collaboration with Subsea 7, Chelsea Technologies Group, QinetiQ and the University of Newcastle.  A series of trials have been conducted to demonstrate the noise and reliability performance of the POSCOM system in acoustically hostile environments.

A typical application located two POSCOM beacons on the seabed in proximity of a pipeline bundle tow out, conducted by Subsea 7 tugs. A receiver system was located on a trials vessel that recorded all acoustic signals throughout the trial. Tug spectral noise density was comparable to standard values derived from a similar class of tug whilst spreading losses within the bay approximate to a 20log r spherical spreading model. .

 POSCOM Beacon

Datasheet - POSCOM

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Applying this data to that gathered during the trial, POSCOM operated successfully in environments displaying signal to noise ratios of between –11dB and –15dB. This compares favourably with predicted theoretical performance.  Furthermore, once tracking POSCOM could operate at even higher levels of background noise.

POSCOM exhibited reliability and repeatability of ranging that would not be achieved by a standard continuous wave positioning system. Indeed, with an already proven range accuracy of better than 5cm rms and an 8km range capability in shallow water with an equivalent source level of 157dB re 1mPa @1m in a 6kHz band, POSCOM can meet the demands of providing an accurate positioning system even in acoustically hostile environments.
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POSCOM Technical Advantage

In terms of noise performance, a pulsed Narrow Band continuous wave (CW) system achieves processing gain by filtering the input signal around the transmission bandwidth. To maximise processing gain, one uses a Narrow Band filter, since this rejects more noise. However this conflicts with the need for the system to have good range resolution. Range resolution is ultimately determined by the transmission bandwidth and so in a conventional Narrow Band CW system the pulses must be short and the receiver bandwidth large to achieve good range resolution. Increasing the receiver bandwidth admits more noise and this in turn reduces the noise performance of the system. The processing gain afforded by a pulsed Narrow Band CW system is unity. Narrow Band CW pulses are subject also to fading in multipath environments that can degrade performance. 

POSCOM implements pulse compression that overcomes these limitations and provides processing gain determined by the bandwidth time (BT) product of the transmission pulse. In such systems the processed signal to noise ratio is improved by a factor of between BT to 2BT depending on the precise implementation of the receiver processing. POSCOM realises a processing gain in the region of 27dB and operates with a detection threshold between 9dB to 15dB depending on environment. The advantage of using digital waveforms over conventional swept sinusoids such as chirps stems from the ability to exploit a wider signal set whose correlation properties are superior to those of chirps, provided they are processed appropriately. This inherently gives the system a data transmission capability plus superior range and Doppler tracking performance. 

POSCOM Capabilities

POSCOM has undertaken several trials during the development program. These include the Wick noise trial, reservoir trials to access range accuracy and a shakedown sea trial in Weymouth Bay. These trials have demonstrated the following capabilities of the POSCOM system.

  • Ability to operate with received acoustic signals approximately –15dB below the noise floor. A significant performance advantage over standard Narrow Band CW positioning systems.

  • Ability to tolerate higher background noise levels once the system is tracking.

  • Reliability and repeatability of ranging in acoustically hostile environment. This performance would not be matched by a standard Narrow Band CW positioning system.

  • Proven range accuracy better than 5cm rms.

Range capability of 8km in shallow water with very low equivalent source level of 157dB re 1mPa @1m in a 6kHz band.

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Chelsea Technologies Group Ltd
55 Central Avenue, West Molesey,
Surrey, KT8 2QZ, UK.
Tel: +44 (0)20 8481 9000    Fax: +44 (0)20 8941 9319
Email: sales@chelsea.co.uk

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©2003 Chelsea Technologies Group - The company reserves the right to alter this specification without prior notice.