Versatile Acoustic Source System (VASS)

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The Versatile Acoustic Source System has been designed and developed to evaluate the performance of a wide range of active and passive sonar. It produces 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 Windows XP interface, VASS allows desktop set-up of complete trials programs in advance, hence avoiding costly errors in signal definition during calibration trials.

 

Existing users of the ERAS & VASS systems include QinetiQ, the UK Director of Submarines, NATO SACLANT Undersea Research Centre, La Spezia, Italy, the Belgian Navy & EDO Corporation, USA.

Applications and Features
Applications
  • Sonar test and calibration
  • Underwater target detection
  • Sonar operator training
  • Surveillance
  • Noise signature simulation
  • At sea, acceptance trials
Features
  • Broadband operation
  • Operator control via computer
  • Self contained and transportable
  • Easily deployed from a range of ocean going vessels
  • Advanced, acoustics source and echo repeat functions
 
Description

The Versatile Acoustic Source System (VASS) is designed to evaluate the performance of a wide range of active and passive sonar. It produces 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 Windows XP 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 reltively small vessels with few facilities 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. This Cabin is a self contained, environmentally controlled, half size ISO container which contains the Computer, Power Amplifier and control electronics for operating the system. All transmissions can be monitored on the system's digital analyzer or via a set of headphones outputs.
Operating Modes
  • Complex Signal Source
  • Sequence
  • Echo Repeater
  • Transponder
  • Received Signal Monitor
  • Slant Range Measurement
The VASS family consists of three main systems:
Full system:
This includes the containerized Surface Operations Cabin, a Winch, a towed body (complete with wide band transducer and hydrophones) and a slant range processing (DME) system. The Surface Operations Cabin includes all of the electronics required to control VASS, and supplementary systems such as printers, radios and a digital analyser.		   Research system:
For research purposes, a slightly less powerful system is available which has the majority of the electronics in the towed body and is controlled by a portable computer.		 Remotely deployable system:
This system is a battery powered version of the research system which can be suspended from a buoy. It is controlled over a radio link by a portable computer.
 
Modes
Source & Sequence Mode
As a calibrated acoustic test signal transmitter (source mode) VASS can generate complex acoustic test signals between 300Hz 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.
Echo Repeat Mode
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.  The many configurable parameters are controlled via an easily operated Graphical User Interface, running under Microsoft Windows 98. Within this interface, the user can add Doppler, target strength and signal highlights to the echo repeated acoustic signal. Subsequent echo repeated signals could, in addition to the above, simulate a moving target track.
Transpond Mode
 In Transpond mode, VASS can transmit a user defined acoustic signal in response to a trigger event which can be either acoustic, from an external input or under operator control. The transpond signal can be defined (300Hz to 12.5kHz only) as a single pulse, or a ramp of pulses, of a monotone or LFM or LPM sweeps, with selectable frequency and source level.  In addition, any selection within the Source Mode can be transponded allowing signals from 300Hz to 200kHz to be transponded.
 
Specification
General Specification  
Modes: Source, Echo Repeat, Transpond, Sequence, Receive
Transmit bandwidth: 300Hz to 200kHz
Source level: Up to 180dB re 1µPa @ 1m (4kHz to 200kHz)
Horizontal beam pattern: Omnidirectional
Source Mode
Pulse lengths: 3ms to 10s or CW (below 17.5 kHz)
Number of pulses: Up to 1000
Pulse intervals: Up to 60s
Variable step levels: -10 to +10dB
Tones: Up to 24 (each with definable source levels and frequencies,
with up to 5 Noise bands - CW or pulsed)
Sweeps: LFM or LPM
Noise: Either broadband or up to 5 user definable bands
Noise types: White, Pink or Pseudo-Random
Modulated signal: AM or FM (user definable carrier and modulating signal)
Echo Repeat Mode
Echo frequency: Broadband (300Hz to 12.5kHz) or  3 narrow bands
Trigger types: Acoustic, TTL pulse or manual
Trigger level and averaging: Fully user definable
Echo length: 10ms to 5s
Added doppler: -40 to +40 knots
Added echo strength: -30 to +40dB
Echo delay: Up to 60s
Highlights: Up to 5
Highlight strength: -30 to +30dB
Relative delay: Up to 200ms
Moving track target : Start range up to 90km Velocity, -40 to +40 knots
Tag on transponder: User configurable
Transpond Mode
Frequency range:

Receive - 300Hz to 12.5kHz    Transmit - 300Hz to 200kHz
Trigger types: Acoustic, TTL pulse or manual
Trigger level and averaging: Fully user definable
Transpond types: LFM or LPM sweep Monotone or as per Source Mode


Sequence Mode
Pulse types: Tones, Noise, LFM or LPM Sweeps, modulated signal or pulse trains
Pulse trains: Up to 1000
Pulse lengths: Up to 10s each
Receive Mode
Frequency range: 300 Hz to 12.5kHz or through band pass filter
Surface Operations Cabin
Size: Half size ISO container (3.0m x 2.4m x 2.4m high)
Power input: 3 phase 380V 50Hz, or 415V 50Hz, or 440V 60Hz
Climate control: Air conditioning and heating
Standard equipment:

19 inch racks containing a complete set of VASS electronics.Includes: DSP card, Band pass filter card, DC/DAC card, MF Power amplifier, HF Power Amplifier, PC,  monitor, Keyboard, Printer, Digital Analyser.


Tow Fish:
Tow speed: 2 to 8 knots
Size: Wingspan: 1.4m Length: 1.4m Height: 0.6m
Weight: 195kg in air
Within tow fish: Transmitting transducers, Receive hydrophone, Monitor hydrophone and tow fish electronics.
Tow Fish Electronics
Telemetry: Pitch, roll, heading, depth and temperature all displayed on the Windows interface in the Surface Operations Cabin and recorded in a log file).
Received hydrophone: Calibrated for receive and echo repeat.
Monitor hydrophone: For monitoring all transmissions
Transmit Transducers
Number: 4
Frequency bands: 300Hz to 17.5 kHz
17.5 kHz to 50 kHz
50 kHz to 110 kHz
111 kHz to 200 kHz
Source level: Up to 180dB re 1mPa @ 1m
Horizontal response: Omnidirectional
Winch
Size: 2m x 1.6m x 1.6m high
Power input: 3 phase 380V 50Hz, or 415V 50Hz, or 440V 60Hz
Tow Cable
Diameter: 12.7mm
Length: 1000
 
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