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An autonomous system for ocean acoustic tomography

P. Felisberto , C. Lopes  and S.M. Jesus
SiPLAB-FCT, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.

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Ref.: Sea Technology, vol.45, no.4, pp.17-23, April 2003.

Abstract : Vertical line arrays (VLA) are a widely used apparatus in underwater acoustic research with applications in target detection and localization, underwater communications, acoustic tomography, acoustic reverberation, etc. Very often the flexibility in water column sampling is achieved by splitting the VLA into modules that can be assembled in different ways according to the application. This kind of systems can be deployed and recovered from small vessels with a shorthanded crew and makes it possible for research labs with reduced budgets and operational means (ships and manpower) to get control over the all development process from data acquisition upto the data post-processing. SiPLAB, a signal-processing laboratory located at the University of Algarve, Portugal, has recently acquired such a system to support its research under the INTMATE project [1]. This system, here below referred as Ultra Light Vertical Array (ULVA), can be configured with up to 16 hydrophones operating in the band 10 -- 2200 Hz, and various non acoustic sensors like thermistors, tiltmeters and pressure gauges.  SiPLAB has successfully used the ULVA in a recent shallow water experiment devoted to shallow water acoustic tomography and communications (INTIFANTE'00 [2]).  In order to overcome the observed drawbacks of the ULVA system SiPLAB has decided to, under a new project called ATOMS,  transform the actual system into an autonomous acquisition system with local storage facilities, lower power consumption, capability of online remote quality control of the acquired data and system positioning information. The new system, named Remote Data Acquisition System (ULVA/RDAS) is based on "open technologies", which are cost effective, allow future upgrade and, as a bonus, relatively easy integration into a tomography network system.  After an overview of the actual ULVA system, the architecture of new ULVA/RDAS system is presented. Follows the evaluation report of the new ULVA/RDAS at sea. Conclusions and future developments are drawn in a final remarks section.

ACKNOWLEDGMENT: this work was partially supported by ATOMS projects (FCT, Portugal).