Point Source Localization Sonar System and Method

• US 20080316862A1
• Filed: 06/25/2007
• Published: 12/25/2008
• Est. Priority Date: 06/25/2007
• Status: Active Grant

• Current Assignee: Government of the United States of America
• Original Assignee: Government of the United States of America
• Inventors: Bernecky, W. Robert, Krzych, Matthew J.
• Granted Patent: US 7,639,565 B2
• Time in Patent Office: Days
• US Class Current: 367/131
• CPC Class Codes: G01S 3/8083 determining direction of source

Abstract

A matched-field based sonar system and method of use that supports real-time, three-dimensional acoustic source localization using a mobile, horizontal array. The system receives and processes acoustic array, non-acoustic array, and own-ship navigational data in the matched-field process (MFP). Driven by own-ship and array status, a global bathymetry database and an acoustic environmental model are used to generate replicas for the MFP. If a three-dimensional tracker is assigned, then the tracker will steer the search region to maintain contact on the target of interest. Displays are provided to the user including tracker displays (which provide tracker information), MFP ambiguity surface displays (which support contact localization), and non-acoustic and navigational displays. A control interface allows a user to control the search region in bearing, range, depth, and frequency; assign the three-dimensional tracker function; and control display processing.

Claims

1. A point source localization sonar system comprising:

a towed hydrophone array adapted to be towed behind a ship for receiving acoustic signals in water via a plurality of hydrophones and outputting acoustic array data;

a plurality of non-acoustic data sensors incorporated in said towed hydrophone array for measurement of forward and aft depth, heading, and temperature and for outputting non-acoustic array data;

a navigational interface on the ship for determining navigation data including heading, depth, speed, latitude, and longitude;

a communication link connecting said towed hydrophone array, said non-acoustic data sensors, and said navigational interface;

a matched-field processor capable of processing the acoustic array data into frequency-wave number data; and

a non-acoustic data processor including a bathymetry database and acoustic environmental model, said non-acoustic data processor capable of processing the non-acoustic array data and navigation data and extracting data from said bathymetry database and said acoustic environmental model to generate replica data.

2. A point source localization sonar system according to claim 1, wherein said plurality of non-acoustic data sensors comprises non-acoustic array data (NAD) sensors.

3. The point source localization sonar system according to claim 1, wherein said plurality of non-acoustic data sensors comprise engineering module (EMODs).

4. The point source localization sonar system according to claim 1, wherein said plurality of non-acoustic data sensors comprises a combination of non-acoustic array data (NAD) sensors and engineering modules (EMODs).

5. The point source localization sonar system according to claim 1, wherein said matched-field processor further comprises a range-focused k-w beamformer and voxel interpolator.

6. A point source localization sonar system comprising:

a towed, horizontal array including acoustic sensors and non-acoustic sensors capable of providing acoustic and non-acoustic data;

a shipboard navigational interface capable of providing own-ship data;

an external interface for receiving the acoustic, non-acoustic, and own-ship data in real-time;

a two-dimensional fast Fourier transform processor for processing said acoustic data;

an acoustic data preparation processor capable of processing the acoustic data into frequency-wave number data;

a non-acoustic data preparation processor capable of processing the non-acoustic and own-ship data to generate replica data;

a global bathymetry database for providing ocean depth under own ship to said non-acoustic data preparation processor for processing the replica data;

an acoustic environmental model capable of processing the replica data;

a matched-field processor including a range-focused beamformer and a voxel interpolator, whereby said matched-field processor is capable of comparing frequency-wave number data with the replica data;

an ambiguity surface collector capable of creating a composite surface;

a three-dimensional tracker capable of accepting the composite surface and tracking a contact;

a plurality of displays capable of providing target motion analysis (TMA) in real-time; and

a communication link connected to said horizontal array, said navigational interface, said external interface, said fast Fourier transform processor, said acoustic data preparation processor, said non-acoustic data preparation processor, said global bathymetry database, said acoustic environmental model, said matched-field processor, said ambiguity surface collector, said tracker, and said plurality of displays.

7. A point source localization sonar system according to claim 6, further comprising a user control interface capable of allowing a user to control said acoustic data preparation processor, said non-acoustic data preparation processor, said plurality of displays, and said tracker.

8. A point source localization sonar system according to claim 7, wherein said plurality of displays comprise non-acoustic array data and navigational displays, matched-field processing displays, and tracker displays.

9. A point source localization sonar system according to claim 8, wherein said non-acoustic array data and navigational displays comprise:

own-ship depth displays, towed array depth displays, towed array cant displays, ocean depth displays, heading displays, and speed displays.

10. A point source localization sonar system according to claim 8, wherein said matched-field processing displays comprise:

a depth versus range display, said depth versus range display capable of showing current depth and range ambiguity surface for a search region;

a range versus bearing display, said range versus bearing display capable of showing current range and bearing ambiguity surface for the search region;

a range-time recorder display, said range time recorder display capable of showing range history of the depth and range ambiguity surface; and

a bearing time recorder display, said bearing time recorder display capable of showing bearing history of the range and bearing ambiguity surface.

11. A point-source localization sonar system according to claim 8, wherein said tracker displays comprise:

a Geographic Situation (GEOSIT) display, said GEOSIT display capable of plotting position of own-ship and contact capable of displaying estimated contact course and speed; and

a tracker history display, wherein said tracker history display is a three-dimensional display capable of plotting tracker bearing, range, and depth estimates as a function of time.

12. A point source localization sonar system according to claim 6, wherein said non-acoustic sensors further comprise non-acoustic array data sensors and engineering modules.

13. A point source localization sonar system according to claim 6, wherein said global bathymetry database is a digital bathymetry database variable resolution.

14. A point source localization according to claim 6, wherein said acoustic environmental model is a multi-path expansion model.

15. A method of point-source localization comprising the steps of:

receiving acoustic array, non-acoustic array, and own-ship navigational data continuously;

preparing frequency-wave number data;

preparing replica data;

determining sound speed at an array;

providing a matched-field processor;

processing frequency-wave number data and replica data in the matched-field processor in real time;

preparing a composite surface; and

tracking a contact.

16. A method of point-source localization according to claim 15, wherein said step of preparing frequency-wave number data comprises the substeps of:

converting acoustic array data into low/medium frequency aperture data with an external interface;

sending aperture data from the external interface to a two-dimensional Fast Fourier Transform;

generating frequency-wave number data with the two-dimensional Fast Fourier Transform;

sending the frequency-wave number data to an Acoustic Data Preparation processor; and

preparing frequencies of interest in the Acoustic Data Preparation processor.

17. A method of point-source localization according to claim 16, wherein said step of preparing frequencies of interest in the Acoustic Data Preparation processor comprises the substeps of:

extracting the frequencies of interest;

normalizing the frequencies of interest;

padding the frequencies of interest; and

sending the frequencies of interest to a beamformer.

18. A method of point-source localization according to 00000000 claim 15, wherein said step of preparing replica data comprises the substeps of:

converting the non-acoustic array data and the own-ship navigational data for system level synchronization with the External Interface;

sending synchronized non-acoustic array data and own-ship navigational data to a 0Non-Acoustic Data Preparation processor;

updating search region to reflect user/tracker initiated changes;

extracting ocean depth under own-ship from a Global Bathymetry Database;

calculating array cant;

calculating array heading;

adjusting bearings in the search region to account for discrepancies between ownership and array headings;

estimating latitude and longitude for the bearings;

extracting ocean depths from the Global Bathymetry Database for every position estimated in said step of estimating latitude and longitude for the bearings;

determining sound speed at each voxel center;

sending own ship depth, array depth, search region parameters, sound speed profile, and information calculated in said steps of updating a search region to reflect changes, extracting ocean depth under own ship from the Global Bathymetry Database, calculating array cant, calculating array heading, adjusting bearing to account for discrepancies between own ship and array headings, estimating latitude and longitude for the bearings, extracting ocean depths from the Global Bathymetry Database for every position estimated in said step of estimating latitude and longitude for the bearings, determining sound speed at each voxel center, to an Acoustic Environmental Model;

generating replicas for the voxel centers in the Acoustic Environmental Model;

sending replicas from the Acoustic Environmental Model back to the Acoustic Data Preparation processor to account for sloping ocean bottoms;

sorting eigenrays of the replicas by signal strength and propagation type in the Non-Acoustic Data Preparation processor; and

sending the replicas from the Non-Acoustic Data Preparation processor to the beamformer.

19. A method of point-source localization according to claim 15, wherein said step of processing frequency-wave number and replica data in the matched-field processor in real time comprises the substeps of:

forming a composite set of eigenrays in the beamformer;

sending the composite set of eigenrays to a voxel interpolator;

generating eigenrays for each voxel center;

phase-shifting the eigenrays;

summing the eigenrays; and

sending output from the voxel interpolator to an ambiguity surface collector.

20. A method of point-source localization according to claim 15, wherein said step of preparing a composite surface comprises the substeps of:

collecting individual voxel ambiguity surfaces in an ambiguity surface collector; and

outputting a composite surface from the ambiguity surface collector to a three-dimensional tracker and a plurality of matched-field processing displays.

21. A method of point-source localization according to claim 15, wherein said step of tracking a contact comprises the substeps of:

inputting the non-acoustic array data, own-ship navigational data, and composite surface into a tracker;

generating a time-averaged estimate of contact bearing, range, and depth;

steering a geographic area of interest;

estimating contact latitude, longitude, course and speed with the tracker;

sending data estimated in said step of estimating contact latitude, longitude, course and speed with the tracker to a plurality of tracker displays;

displaying tracker bearing, range, and depth estimates on a plurality of displays of the matched-field processor;

forwarding the non-acoustic array data and own-ship navigational data from a Non-Acoustic Data Preparation processor to a plurality of non-acoustic array data and navigational displays; and

evaluating the non-acoustic array data and navigational displays, the displays of the matched-field processor, and the tracker displays for point source localization of a contact.