Accession Number : ADA262325


Title :   VLF Source Localization with a Freely Drifting Acoustic Sensor Array


Descriptive Note : Final rept. Jun 90-Jun 92


Corporate Author : NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA


Personal Author(s) : Chen, G C


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a262325.pdf


Report Date : Sep 1992


Pagination or Media Count : 157


Abstract : The objective of this study is to demonstrate the source localization and tracking capability of the freely drifting Swallow float volumetric array with the matched-field processing (MFP) technique using data collected during the 1989 Swallow float experiment conducted in the Northeast Pacific. A set of nine freely drifting, infrasonic sensors, capable of recording ocean ambient noise in the 1- to 25-Hz range, was deployed to span the water column of 4100-m depth, with horizontal aperture on the order of 5 km. Even though the floats were freely drifting, their positions were determined with the 8-kHz internal navigation system and a postprocessing least-squares-based localization procedure. The rms position error estimated by the float localization procedure is less than 5 meters, which is within the desired accuracy of one-tenth of a wavelength at the highest frequency of interest, 25 Hz (6 m), in order to effectively beamform the acoustic data. Analysis of the acoustic data showed high signal-to-noise ratio and high magnitude-squared coherence at 14 Hz among all floats during some time intervals. The 14-Hz was a continuous wave (cw) tone projected by a source of opportunity deployed about 2500 km from the Swallow float array. The high coherence among the floats provided an opportunity to matched-field process the acoustic data. The replica pressure field was modeled with an adiabatic normal-mode numerical technique using the environmental data collected during the experiment.


Descriptors :   *ACOUSTIC ARRAYS , *ACOUSTIC DATA , *ACOUSTIC DETECTORS , DATA PROCESSING , OCEAN SURFACE , SIGNAL TO NOISE RATIO , KALMAN FILTERING , DEPTH , FLOATS , DRIFT , LEAST SQUARES METHOD , BEAM FORMING , HYDROPHONES , AMBIENT NOISE , SONAR TRANSDUCERS , TRAVEL TIME , VERY LOW FREQUENCY , GEOPHONES


Subject Categories : Acoustic Detection and Detectors


Distribution Statement : APPROVED FOR PUBLIC RELEASE