NDLI: An autonomous underwater vehicle towed array for ocean acoustic measurements and inversions

Content Provider	IEEE Xplore Digital Library
Author	Holmes, J.D. Carey, W.M. Lynch, J.F. Newhall, A.E. Kukulya, A.
Copyright Year	2005
Description	Author affiliation: Dcpt. of Aerosp. & Mech. Eng., Boston Univ., MA, USA (Holmes, J.D.; Carey, W.M.)
Abstract	A novel experimental method involving an autonomous underwater vehicle (AUV) with a towed hydrophone array has been developed to measure the single path interaction from the surface, bottom and volume of the shallow water waveguide. The system is designed to operate from the low (/spl sim/100 Hz) to the mid frequencies (/spl les/10 kHz) with a directional source. The effects of surface, volume, and bottom scattering on the coherency of direct and direct-reflected signals are difficult to measure and a mobile directional receiver provides an adaptive capability. For example, the quantification of the role micro-bubble layers near the surface and in surface ship wakes plays on the coherency and scattering of sound could be measured with this device. In addition, an AUV with a hydrophone array can be easily and rapidly deployed and because of its mobility can provide area wide characterization. However, AUV radiated noise measurements indicated vehicle noise would limit the ability of hull-mounted or interior hydrophone arrays and thus suggested the use of a low noise towed array. The AUV discussed here is the Remus vehicle, a tested as well as a readily-available tow platform for a small low drag array. To demonstrate the ability of Remus to act as a low noise tow vehicle, radiated noise measurements were made on the vehicle at Dodge Pond acoustic test facility. The vehicle was rotated on a shaft at a depth of 8 meters and calibrated noise levels measured at 13 meters distance. At the maximum rpm of the AUV, the 1/3/sup rd/ octave noise level, when converted to source level by the calibrated transmission factor, was 130 dB re 1/spl mu/Pa at 1 m. This would represent the radiated noise source level for a vehicle moving at 3 knots. A small-diameter (2.8 cm O.D.) fluid-filled hydrophone array has been developed with 6 channels spaced evenly at 0.75 meters, each channel having a receiving sensitivity of -174 dB re 1/spl mu/Pa/V from 100 Hz to 10 kHz. The recording system consisted of three commercial off-the-shelf (COTS) battery powered mini-disc recorders with a 20 kHz band pass, sampling frequency of 44 kHz and a 16 bit analog to digital converter providing storage capability of 90 minutes of raw data. The prototype system was deployed in a "proof-of-concept" test at the Dodge Pond test facility. The vehicle was programmed to navigate along paths that provided straight courses as well as several turns to determine the operational characteristics of the system. Results on capabilities of the vehicle with the towed system are presented including vehicle and array noise, beamforming, and element localization.
Starting Page	1058
Ending Page	1061
File Size	814703
Page Count	4
File Format	PDF
ISBN	0780391039
DOI	10.1109/OCEANSE.2005.1513204
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2005-06-20
Publisher Place	France
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Underwater vehicles Acoustic arrays Oceans Acoustic measurements Sonar equipment Sea measurements Sea surface Acoustic noise Noise measurement Noise level
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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