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- The acoustic oceanographic buoy. A light acoustic data acquisition systemPublication . Soares, C.; Zabel, F.; Martins, C.; Silva, A.; Jesus, S. M.The Acoustic Oceanographic Buoy (AOB) is a light acoustic receiving device that incorporates acoustic and non-acoustic signals received in various channels along a vertical line array that provide oceanographic and environment measurements all of which are uniquely GPS time referenced. The physical characteristics of the AOB, in terms of size, weight and autonomy, will tend to those of a standard sonobuoy with, however, the capabilities: of local data storage, dedicated signal-processing, GPS self localizing, real-time monitoring and online data transmission.
- AOB - an easily deployable, reconfigurable and multifunctional acoustic-oceanographic systemPublication . Jesus, S. M.; Soares, C.; Silva, A.; Hermand, J.-P.; Coelho, E.The concept of an easy to use and easy to deploy ocean acoustic tomographic OAT system is presented. The system is composed of a network of buoys and a data inversion online processor. This study concerns the individual node of that network—the acoustic-oceanographic buoy AOB —the data inversion technique and the testing of the system at sea. The AOB is a lightweight surface buoy with a vertical array of acoustic and temperature sensors to be hand deployed in a free-drifting configuration from a small boat. The data are locally stored and transmitted online to a remote station for processing and monitoring. Data inversion is based on a broadband matched-field tomography technique where known and unknown parameters are simultaneously searched for focalization . In situ recorded temperature data serve for algorithm initialization and calibration. The AOB was successfully deployed in several consecutive days during two rapid environmental assessment sea trials in 2003 Mediterranean and 2004 Atlantic . Data collected at sea also show that the AOB can be reconfigured as a receiving array for underwater coherent communications in the band up to 15 kHz.
- Acoustic maritime rapid environmental assessment 2004 during the MREA'04 sea trialPublication . Jesus, S. M.; Soares, C.; Felisberto, P.; Silva, A.; Farinha, L.; Martins, C.Environmental inversion of acoustic signals for bottom and water column properties is being proposed in the literature as an interesting concept for complementing direct hydrographic and oceanographic measurements for Rapid Environmental Assessment (REA). The acoustic contribution to REA can be cast as the result of the inversion of ocean acoustic properties to be assimilated into ocean circulation models specifically tailored and calibrated to the scale of the area under observation. 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 operational Acoustic REA (AREA). The Acoustic Oceanographic Buoy (AOB) was proposed as an innovative concept that responds to the operational requirements of AREA. That concept includes the development of water column and geo-acoustic inversion methods being able to retrieve environmental true properties from signals received on a drifting network of acoustic-oceanographic sensors - the AOBs. An AOB prototype and a preliminary version of the inversion code, was tested at sea during the Maritime Rapid Environmental Assessment 2003 (MREA’03) sea trial and was reported in [1]. On a separate register it should be noted that the characterization of the environment between the source and the receiver also contributes to the identification of the acoustic channel response and therefore provides a basis for fulfilling the objectives of project NUACE1. The present report describes the data sets and results gathered during the MREA’04 sea trial that took place from 29 March to 19 April 2004 off the west coast of Portugal, south of Lisboa (Portugal), with the objectives of testing an improved version of the individual AOB and its functionality in a simple network. The acoustic part of the experiment lasted for four days between April 7 and April 10, 2004 and involved the transmission and reception of pre-coded signals along range-dependent and range-independent acoustic tracks.
- On the applications of a compact autonomous acoustic recorderPublication . SOARES, CRISTIANO; Martins, Celestino; Zabel, Friedrich; Silva, A.A number of acoustic A compact acoustic recorder, primarily designed for underwater noise monitoring, is presented in this paper. The Self-Register Hydrophone has been used in several occasions during the past three years, in underwater noise monitoring activities. However, this kind of device also find application in other areas such as array processing and passive acoustic monitoring of marine mammals. An overview on the application of the Self-Register Hydrophone is given herein.
- INTIFANTE'00 sea trial data report - Events I,II and IIIPublication . Jesus, S. M.; Silva, A.; Soares, C.This report describes the data acquired during Events I, II and III of the INTIFANTE'00 sea trial, that took place from 9 - 29 October 2000, o the Tr oia Peninsula, near Set ubal, Portugal.
- Acoustic Oceanographic Buoy testing during the Maritime Rapid Environmental Assessment 2003 sea trialPublication . Soares, C.; Jesus, S. M.; Silva, A.; Coelho, E.This paper proposes an innovative concept that responds to the requirements of acoustic REA as the integration between a network of sophisticated Acoustic-Oceanographic Buoys (AOB) and online ocean properties inversion algorithms. A prototype of the system, in- cluding one sonobuoy and a preliminary version of the inversion code, was tested at sea during the MREA'03 sea trial. The AOB is a light acoustic receiving device that in- corporates last generation technology for acquiring, storing and processing acoustic and non-acoustic signals received in various channels along a vertical line array. During the MREA'03 the AOB was deployed on a free drifting con guration. Source/receiver geom- etry was estimated from the buoy's GPS. Online processing was made possible by wireless transfer of the data and inversion was done in a range-dependent environment. Temper- ature pro les inverted from acoustic signals in two frequency bands on near
- Acoustic Oceanographic Buoy Test during the MREA’03 Sea TrialPublication . Jesus, S. M.; Silva, A.; Soares, C.Environmental inversion of acoustic signals for bottom and water column properties is being proposed in the literature as an interesting concept for complementing direct hydrographic and oceanographic measurements for Rapid Environmental Assessment (REA). The acoustic contribution to REA can be cast as the result of the inversion of ocean acoustic properties to be assimilated into ocean circulation models specifically tailored and calibrated to the scale of the area under observation. 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 operational Acoustic REA (AREA). An innovative concept that responds to the operational requirements of AREA is being proposed under a Saclantcen JRP jointly submitted by the the Universit´e Libre de Bruxelles (ULB), SiPLAB/CINTAL at University of Algarve, the Instituto Hidrogr´afico (IH) and the Royal Netherlands Naval College (RNLNC) and approved by Saclantcen in 2003 under the 2004 SPOW. That concept includes the development of water column and geo-acoustic inversion methods being able to retrieve environmental true properties from signals received on a drifting network of Acoustic-Oceanographic Buoys (AOB). A prototype of an AOB 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 report together with the results obtained.
- Measuring underwater noise with high endurance surface and underwater autonomous vehiclesPublication . Silva, A.; Matos, A.; Soares, C.; Alves, J. C.; Valente, J.; Zabel, F.; Cabral, H.; Abreu, N.; Cruz, N.; Almeida, R.; Ferreira, R. N.; Ijaz, S.; Lobo, V.This paper describes the results of AcousticRobot'13 - a noise measurement campaign that took place off the Portuguese Coast in May 2013, using two high endurance autonomous vehicles capable of silent operation (an underwater glider and an autonmomous sailing vessel) equipped with hydrophones, and a moored hydrophone that served as reference. We show that the autonomous vehicles used can provide useful measurements of underwater noise, and describe the main advantages and shortcomings that became evident during the campaign.
- AOB - Acoustic Oceanographic Buoy: concept and feasibilityPublication . Jesus, S. M.; Soares, C.; Silva, A.; Hermand, J.-P.; Coelho, E.The AOB - Acoustic Oceanographic Buoy is the single node of a network of “smart” buoys for acoustic surveillance, Rapid Environmental Assessment (REA) and underwater communications. The AOB is a lightweight surface buoy with a vertical array of acoustic receivers and temperature sensors to be air dropped or hand deployed from a small boat. The received data is geotime and GPS precisely marked, locally stored and processed by on board dedicated DSP hardware. AOBs can exchange data over a local area network that includes submerged, sea surface (like for instance other AOBs) and air or land located nodes, allowing for the integration of all users in a seamless network. Specific software allows AOB usage in complex tasks such as passive or multistatic acoustic surveillance, acoustic observations for REA oceanographic forecast and model calibration, bottom and water column acoustic inversion, underwater communications and cooperating target tracking. The AOB was successfully deployed in several consecutive days during two Maritime REA sea trials in 2003 (Mediterranean), in 2004 (Atlantic) and for an high-frequency underwater communications experiment during MakaiEX, 2005 (Hawai). Data collected at sea shows that the AOB is a versatile, robust and easy to use tool for a variety of broadband underwater acoustic applications.