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Hydrophones Projectors Echo Sounders Sidescan Sonar Telemetry & Acoustic Releases Custom Design Calibration |
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The Versatile Acoustic Source System (VASS) has been designed and developed by Chelsea Technologies Group to evaluate the performance of a wide range of active and passive sonars. It can produce complex calibrated transmissions in addition to echo repeating, transponding and acting as a calibrated receiver. VASS provides a highly versatile and flexible sonar test system which is configured by simple mouse or keyboard selections. In addition to instant configuration changes, via its Microsoft Windows 98TM interface. VASS allows desktop set-up of complete trials programs in advance hence avoiding costly errors in signal definition during calibration trials. VASS can be deployed from relatively small vessels with few facilities required other than power and a crane or A frame. The transducers are contained within a compact and robust tow fish that is connected to a lightweight tow cable. On the surface are a winch and a Surface Operations Cabin. The Surface Operations Cabin is a self contained, environmentally controlled, half size ISO container which contains the Computer, Power Amplifier, and DSP electronics for operating the system. Within this cabin, all transmissions can be monitored on the system's digital analyser or headphone outputs. |
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Features
Existing
users of the ERAS, VASS & PERS systems include QinetiQ, the UK
Director of Submarines, NATO SACLANT Undersea Research Centre, La Spezia,
Italy, the Belgian Navy & EDO Corporation, USA
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The
VASS family consists of three |
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Full
system: |
Research
system: |
Remotely
deployable system: |
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Complex
Signal Source: Calibrated Acoustic |
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As a calibrated acoustic test signal transmitter (source mode) VASS can generate complex acoustic test signals between 30Hz and 200kHz at source levels of up to 185 dB re 1µPa@1m. It is capable of concurrently generating up to 24 tones. The system can also generate simultaneous wide band noise (selectable bands according to transducer) or five narrow noise bands (selectable from white, pink or pseudo-random noise). The frequency and source level of each tone (and noise band) may be controlled independently and each selected as CW or pulsed. VASS can also generate LFM or LPM sweeps and complex modulated acoustic transmissions (AM or FM). The sequence mode allows the user to program a series of pulse trains giving up to 12,500s of continuous programmed sequenced transmissions, for example 250 uniquely specified pulse trains each with 1000 50ms pulses can be specified. |
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General Specification |
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Modes: |
Source, Echo Repeat, Transpond, Sequence, Receive |
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Transmit Bandwidth: |
30Hz to 200kHz |
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Source Level: |
Up to 185dB re 1µPa @ 1m (3kHz to 200kHz) |
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Horizontal Beam Pattern: |
Omnidirectional |
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Source Mode |
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Pulse lengths: |
3ms to 10s or CW (below 17.5 kHz) |
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Number of pulses: |
Up to 1000 |
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Pulse intervals: |
Up to 60s |
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Variable step levels: |
-10 to +10dB |
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Tones: |
Up
to 24 (each with definable source levels and frequencies, |
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Sweeps: |
LFM or LPM |
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Noise: |
Either broadband or up to 5 user definable bands |
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Noise types: |
White, Pink or Pseudo-Random |
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Modulated signal: |
AM or FM (user definable carrier and modulating signal) |
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In
Echo Repeat mode, VASS can repeat acoustic signals (between 300Hz and
12.5kHz) sampled from the dedicated receiver hydrophone contained in the
towed body. It does this in response to a trigger event, based either on
the incoming acoustic signal, an external input, or under operator
control. The repeated signal can have a highlight structures and Doppler
shift imposed upon it to mimic the reflections from a moving or
stationary target. |
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Echo Repeat Mode |
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Echo frequency: |
Broadband (300Hz to 12.5kHz) or 3 narrow bands |
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Trigger types: |
Acoustic, TTL pulse or manual |
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Trigger level and averaging: |
Fully user definable |
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Echo length: |
10ms to 5s |
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Added doppler: |
-40 to +40 knots |
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Added echo strength: |
- 30 to +40dB |
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Echo delay: |
Up to 60s |
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Highlights: |
Up to 5 |
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Highlight strength: |
-30 to +30dB |
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Highlight offset: |
Up to 200ms |
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Moving track target : |
Start range up to 90km Velocity, -40 to +40 knots |
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Tag on transponder: |
User configurable |
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Transponder
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Transpond Mode |
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Frequency range: |
Receive
- 300Hz to 12.5kHz |
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Trigger types: |
Acoustic, TTL pulse or manual |
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Trigger level and averaging |
Fully user definable |
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Transpond types: |
LFM
or LPM sweep Monotone |
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Sequence Mode |
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Pulse Types: |
Tones, Noise, LFM or LPM Sweeps, modulated signal or pulse trains |
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Pulse Trains |
Up to 1000 |
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Pulse Lengths: |
Up to 10s each |
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In receiver mode, VASS can act as a fully calibrated underwater acoustic signal receiver (between 300Hz and 12.5kHz) via a hydrophone mounted in the towed body. This receiver is also used for the echo repeat and transpond functions of VASS. |
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Receive Mode |
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Frequency Range: |
300 Hz to 12.5kHz or through band pass filter |
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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 & 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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Slant Range (DME) System: |
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Type |
Synchronised ranging system |
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Frequencies: |
Selectable depending on the vessel's sonar |
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Synchronised: |
Via VHF radio to vessel under test |
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Oscillator: |
Highly stable oven controlled oscillator |
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Remote DME System: | |
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PC: |
Portable mains powered PC with LCD screen |
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Cards included in PC: |
DME processor and DME DSP card |
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Software |
Remote DME User Interface, running under Microsoft Windows 95-98 |
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Printer: |
Portable ink jet |
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Interface to sonars: |
Transmit via (for example) underwater telephone system or separate transducer(s). Receive via a suitable sonar's bus (with a separate interface unit) or underwater telephone or separate transducer(s). |
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Synchronisation: |
Interface to vessel's VHF radio set |
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Surface Operations Cabin: | |
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Size |
Half size ISO container (3.0m x 2.4m x 2.4m high) |
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Power input: |
3 phase 380V 50Hz, or 415V 50Hz, or 440V 60Hz |
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Climate control: |
Air conditioning and heating |
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Standard Equipment: |
Two 19 inch racks containing a complete set of VASS electronics and a complete backup set. Each set includes: DSP card, Band pass filter card, DC/DAC card, DME processor card, DME DSP card, 1.2kVA Power amplifier, HF Power Amplifier, Pentium PC, 14" monitor, Keyboard, Printer, VHF Radio, Digital Analyser. |
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Tow Fish: |
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Tow speed: |
2 to 8 knots |
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Size |
Wingspan: 1.4m Length: 1.4m Height: 0.6m |
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Weight: |
195kg in air |
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Within tow fish: |
Transmitting transducers, Receive hydrophone, Monitor hydrophone and tow fish electronics. |
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Tow Fish Electronics |
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Telemetry: |
Pitch, roll, heading, depth and temperature all displayed on the Windows interface in the Surface Operations Cabin and recorded in a log file). |
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Received Hydrophone: |
Calibrated for receive and echo repeat. |
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Monitor Hydrophone: |
For monitoring all transmissions |
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Transmit Transducers | |
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Number: |
4 |
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Frequency bands: |
30Hz to
17.5 kHz |
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Source level: |
Up to 185dB re 1mPa @ 1m |
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Horizontal response: |
Omnidirectional |
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Winch |
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Size: |
2m x 1.6m x 1.6m high |
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Power input: |
3 phase
380V 50Hz, or 415V 50Hz, or 440V 60Hz |
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Tow Cable |
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Diameter: |
12.7mm |
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Length: |
1000 |
