VLF Source Localization with a Freely Drifting Acoustic Sensor Array
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1992
- Accession Number
- ADA262325
Entities
People
- G. C. Chen
Organizations
- Naval Command, Control and Ocean Surveillance Center