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Acoustic Oceanographic Buoy testing during the Maritime Rapid Environmental Assessment'2003 sea trial

S.M. Jesus, C.Soares,  A. Silva , and
SiPLAB-FCT, Universidade do Algarve
Faro, Portugal
E. Coelho
NATO Undersea Research Centre
La Spezia, Italy

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Ref.: Proc. of ECUA' 2004, (ISBN:90-5986-079-9), p.271-279, Delft (The Netherlands), June 2004.

Abstract : Rapid Environmental Assessment (REA) is a goal to which acoustics can give a significant contribution. That contribution can be cast as the result of the inversion of ocean acoustic properties from the propagation of acoustic signals. Traditional ocean tomography systems and methods for their requirements of long and well populated receiving arrays and precise knowledge of the source/receiver geometries are not well adapted to Acoustic REA (AREA). An innovative concept to respond to the AREA requirements is being proposed as an integration between a network of sophisticated Acoustic-Oceanographic Buoys (AOB) and algorithms for online ocean properties inversion. A prototype of the system, including one sonobuoy and a preliminary version of the inversion code, was tested at sea during the Maritime Rapid Environment Assessment'2003 sea trial (MREA'03) and is described in this paper together with the results obtained. The AOB is a light acoustic receiving device that incorporates last generation technology for acquiring, storing and processing acoustic and non-acoustic signals received in various channels along a vertical line array. The physical characteristics of the AOB, in terms of size, weight and autonomy, will tend to those of a standard sonobuoy, with however the capability of local data storage, processing and online transmission. During the MREA'03 the AOB was deployed at two occasions, during several hours, on a free drifting configuration. Source/receiver geometry was estimated from the  on the buoy GPS, that served also to precisely time mark the acoustic signals. On line processing was made possible by wireless transfer of the data and inversion in a complex range-dependent environment. Temperature profiles inverted from acoustic signals in two frequency bands on near real time are shown to approximately agree with concurrent CTD measurements.

ACKNOWLEDGMENT: this work was partially supported by FUP/Ministry of Defence  program under project LOCAPASS and AOB - REA Joint Research Project.