AWACSSW 06 Sea Tests RV Endeavor Cruise 425

AWACS/SW 06 Sea Tests: RV Endeavor Cruise #425 24 August – 10 September, 2006 Phil Abbot, OASIS Inc Jim Lynch and Glen Gawarkiewicz, WHOI John Joseph, NPS 31 January 2007 ONR Progress SW 06 Meeting San Diego, CA

Objectives for SW 06 Sea Tests Build and test components and algorithms for an AWACS of quiet targets operating in complex, littoral, shallow water environments • Conduct high resolution acoustic measurements in the variable shelfbreak environment • Evaluate effects of the environment on acoustic propagation uncertainty and detection characteristics – Horizontal isotropy and invariance – Spatial-temporal dependence, frequency dependence • Use adaptive sampling techniques to reduce uncertainty in the ocean and acoustic fields

OMAS -- Key Workhorse in AWACS/SW 06 For TL and Surrogate Target Detection OMAS Transmission Summary: 550 – 650 Hz and 800 – 1000 Hz 3 x 2 sec, HFM Slides, 1 min rep rate, 700 – 1, 000 Hz CW Depths: 35 – 60 m 9 Runs, 6 – 8 hrs/run Tracking/TL Measured Via Multiple Sonobuoys (LBL) Extensive Spatial Diversity

OMAS Measured Tracks During AWACS/SW 06 7. 5 nmi OMAS Tracks based on Objective Maps and Ocean Adaptive Sampling of Environmental Keys (cross-shelf position, cold pool duct, mixed layer depth)

Temperature field objective map from 12 th Scanfish survey (provided by A. Shcherbina, WHOI). Contour plot at the bottom is from 40 m depth. 80 m isobath Mixed layer depth considerably deeper off shore Shelfbreak front extends seaward over upper slope Shelfbreak front moved seaward after TS Ernesto

AWACS/SW 06 TL Example: Horizontal Isotropy and Translational Invariance Tests TL (PMFO) @ R = 7. 5 km, f=900 Hz 7. 5 nmi OMAS 1 OMAS 2 SB Front Shelfbreak Front – Obj. Map TL @ R = 7. 5 km, f=900 Hz TL means robustly constant except where interacting with Shelfbreak Front. SB Front

Sonobuoy Detection of OMAS Energy Detect BTR 0 Post Processing Peak Energy Detection OMAS Scissorgram OMAS FM Sweeps Time (min) 5 10 15 OMAS Tones 20 25 0˚ 360˚ 0˚ Bearing 360˚ 0 Bearing OMAS Track 500 R/V Endeavor Track 1000 Frequency Bin 1500 2000

Analyses Plans/Needs • Analyses/Papers in collaboration with AWAC PIs, and Others? – Horizontal Isotropy/Invariance – Propagation Through/Along SB Front – Propagation to WHOI Fixed Receivers • Needs – Internal Wave Field Observations During Acoustic Tests – Sea Surface Observations – Bottom Characterization in Area, Including Improved Geo-acoustic Models – Ocean Characterization with Scanfish – Fixed Receiver Time Series – More? Cruise Reports Bundled and Available Upon Request

Backups

Challenges • Safely deploy/recover AUVs w/towed arrays in 46 foot seas (<20 knots wind speed) • Autonomously detect targets, then • Pass information though the ACOMMS link • Develop vehicle command/control methods based on adaptive sampling • Explore limits of signal processing, with emphasis placed on dynamic array control

Summary of AWACS/SW 06 Built and tested components and algorithms for AWACS system • Conducted high resolution oceanographic and acoustic measurements in the New Jersey shallow water environment – 12 Scanfish surveys (>160 hrs) characterizing the Shelfbreak Front variability – 9 OMAS Acoustic tests (>60 hrs) characterizing the effects of the SB front on acoustic propagation, including detection performance • Performed Adaptive Sampling to resolve SB Front and exploited it for improved acoustic transmissions. Objective maps, combined with Data Assimilation at shore, provided sampling ideas – Demonstrated sensitivity to source/receiver depth (6 d. B improvement) – Transmissions along/through the front • Quantified regions of TL uncertainty (scales for horizontal isotropy and translational invariance) • Early Nov. tests planned to deploy TAs off the glider and REMUS vehicles in SW near the Vineyard

Slocum Glider w/OASIS Towed Array Dummy TA in HI (May 06); OTA Calibrated in Dodge Pond, and Integrated with Glider at Webb and WHOI REMUS in Aug. 06

Autonomous Wide Aperture Cluster for Surveillance (AWACS) Concept

Adaptive Sampling • “Maximum Bearings”- An adaptive survey was run with 4 separate transects through a single point at the front to get 8 separate bearings for comparisons with circular OMAS trajectory • “Streamwise Coordinates”- One adaptive survey was run oriented along the axis of the front, to ensure that any sharp curvature of the front downstream of the release point of the sonobuoys was accounted for

AWACS Towed Arrays • WHOI – WTA • • 32 Hydrophone, 16 channels Cut to 1. 0 k. Hz (P = /2) 24 Bit ADC, Variable Sample Rate Data stored on hard drive (120 GB? ) – PTA • 12 hydrophone, 3 x 2 channels • Cut to 1. 0 KHz • Data stored on 3 (x 2 channels) Sony Mini-Disk Recorders • OASIS (OTA) – – 32 Hydrophone, 16 channels Cut to 1. 0 k. Hz (P = /2) 24 Bit ADC, Selectable Sample Rate Data stored on 3 Compact Flash Disks (3 x 4 GB) or Hard Drive (30 GB) – 1. 1” Diameter, Gel-Filled Hose – L(Array Section) = 12. 9 m, L(Leader) = 9. 4 m

SLOCUM Glider, OASIS Towed Array (OTA) and OMAS on the Endeavor During In-Air Shakedown Glider Towed Dummy Array in HI, May 06. OTA Calibrated in Dodge Pond June 06, then Integrated with Glider at Webb and WHOI REMUS in Aug. 06

OASIS TA Integration with AWACS AUVs Integration w/REMUS at WHOI Buoyancy Tests at Webb