Accession Number:

ADA327295

Title:

Near Canopy Arctic Acoustic Backscattering Study.

Descriptive Note:

Final rept. May 1993-Sep 1994

Corporate Author:

WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB

Personal Author(s):

• Ewart, Terry
• Henyey, Frank
• Olson, Leroy
• Williams, Kevin

Report Date:

1994-09-01

Pagination or Media Count:

8.0

Abstract:

We collected under-ice backscattering data with a low frequency 400 Hz, spatially diverse, transmitting and receiving array during the ONR SIMI project in Spring 94. The experiment, termed IBEX Ice Backscattering Experiment was based on the idea that such arrays of sources and receivers can be used to make images of backscattered sound when the geometry is very well known. The data has been processed using interferometric time delay imaging to localize high scattering regions. The measurements were made in two locations one directed at imaging a large ridge, the other directed at imaging an 1000 m diameter expanse of a single floe. The measurements were carried out using several pulse types. We also operated a hyperbolic noise event tracking system to locate ice-cracking events and initiate an imaging sequence. The noise levels and activity were so low during the experiment period, that this feature could not be utilized. The ridge imaging was a collaborative effort with the MIT Group under the direction of Hendrik Schmidt. We have not received the MIT data for the combined effort at this writing.

Descriptors:

• *ACOUSTIC IMAGES
• *BACKSCATTERING
• *UNDERICE
• ACOUSTIC TRACKING
• ARRAYS
• ICE MECHANICS
• INTERFEROMETRY
• LOW FREQUENCY
• PULSE TRANSMITTERS
• RECEIVERS
• SEA ICE

Subject Categories:

• Snow, Ice and Permafrost
• Acoustic Detection and Detectors

Distribution Statement:

APPROVED FOR PUBLIC RELEASE