Acoustic Seaglider Results from Summer 2006

Bruce M. HoweApplied Physics Laboratory University of Washington

ONR CODE 32 NW REGIONAL PROGRESS REVIEWApplied Physics Laboratory, University of Washington

27 February – 1 March 2007Seattle, WA

Goals and Outline

• Develop and demonstrate the acoustic Seaglider in the persistent surveillance context:– As a communications gateway between subsurface

platforms and land– To act as a general purpose acoustic receiver/tactical

sensor for all signals and “noise”, with near-real time reporting of processed results

– To provide oceanographic data

• Review results from 3 field experiments• Discuss next steps

Acoustic Seaglider

• ½ knot at ½ W• Up to 1000 m dives• > 6 months, 3000 km,

600 dives• Temperature, salinity

and others• Now with hydrophone

and acoustic modemFumin Zhang

Philippine Sea

Kauai

Monterey Bay

Acoustic Seaglider Operations – Summer 2006

Philippine Sea – SG022, 7/29/06-7/30/06, 1 day, 15 dives, low ARS band,CTDMonterey Bay – SG022, 8/15/06-8/21/06, 6 days, 61 dives, low ARS band,CTD SG023, 8/18/06-8/23/06, 5 days, 83 dives, low ARS band, CTD SG106, 8/12/06-8/18/06, 6 days, 131 dives, high + low ARS bands,CTD,modemKauai - SG023, 8/31/06-10/8/06, 39 days, 143 dives, low ARS band, CTD

Monterey Bay 06:Positions where SG106 read modem FSK packets

• Black circles: SG106 at surface after dive - no acomms received

• Blue circles: dives where acomms commands logged

• 106 sent FSK command to turn off the ARL-UT array

• Most FSK came from ARL-UT or Gateway

• Black +: dives after recording acomms logs ceased

• 4-5 km ranges are evident

First FSK packet at 2006.08.15:0857 (UTC) from unit ARL-UT to Gateway, Dive 22.

1 km

ARL-UT bottom node

Gateway

Kelp Array

Lat

itud

e

MB06: RXD receptions vs range and depth

Histograms of depths for RXD receptions

C

ount

s0

1

0

20

3

0

40

0 50 100 depth(m)

0 20 40 60 80 100 120 140 depth (m)

C

ount

s0

2

0

40

6

0

SG106 descending SG106 ascending

Depth

0 m

100 m

5 km0 km Range

10 20

10 20

Time (s)30

30

25

20

15

10

5

Fre

q (k

Hz)

Modem performance: 1st 30 sec of dive 41

30

PSD @ 8-10 sec

0 5 10 15 20 25 30 35 kHz

Simple ACOMMS detector: ratio of energy in23-27 kHz band to energy in 15-19 kHz band

glider pump noise

ACOMMS band – 23-27kHzReference band – 15-19kHz

{

telling kelp to talk to GB

from kelp to GBtelling UT-VS to talk to GB

Missed packet

Missed packet

21:24:14 UTC

Frequency

Time (s) 150

~10 nm from shipDive 13, file 2

0

Distant source

Ship source, harmonics and reverb

SignalsExample of Lubell source recorded at SG023(dive 20 segment 2)

LWAD

MB06

NPAL / ATOC Kauai source

• 260 W• M-sequence coded

signals• 75 Hz, 35 Hz bandwidth• 28 ms peak• 27.28 s period• 2 hour transmissions,

1 per dayDIVE 56 -example

30

79

Red segments = ARS recordings

10

.8 m

s

}1

4.7

ms

}1

3.0

ms

}

}

1/75 Hz = 13.3 msExample time series

Example PSD

zoom PSD

Kauai example

Motion and Coherent gain

Doppler + stack:• from 35 to 44 dB• 9 dB of gain • vs theoretical gain 14 dB• Variation during 12 minutes

Time – 12 minutes

Relative travel time – 0.4 s Relative travel time – 0.16 s

Relative travel time – 0.4 s

Time – 12 minutes

Doppler

Arrival times(72.7195)

(72.282)

(72.8654)(72.9153)

(73.4143)

Single block 27.28 s

Peaks shift due to changing s/r range•Measured travel time changes

•~3.7 ms per block•Match glider kinematics

•0.204 m/s, 136 m horizontal, 33 m vertical, 12 minutes

kHz

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

s0 2 4 6 8 10 12 14

humpbackHz

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

105

110

115

s0 5 10 15 20 25 30 35 40 45

3rd harmonic ~48 Hz

1st harmonic ~16 Hz

Blue whale ‘B’ call

Hz

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

105

110

115

s0 5 10 15 20 25 30 35 40 45

Blue whale ‘D’ call

Humpback (very close)

Blue whale

Sea lions?birds

Humpback @ 15 and 65 secBlue @ 35 secSea Lions? @ 50 sec

Animal sounds recorded on Seaglider ARS Monterey Bay, MB06

Ambient noise levels compared to Wenz

ASG – Summer 2006 Summary

• Demonstrated gateway capability – connecting subsurface platforms to shore via acoustic modem/satellite Iridium

• Demonstrated acoustic receiver – man-made signals, whales, noise… with near-real time processed results

• Potential – general ocean acoustics tool, tactical sensors, navigation/time node, data truck, marine mammal observing, tomography receiver, basin-scale thermometry, climate change, …

Next steps• Fall 07 – PLUSNet07 off La Jolla

– Spring/summer – mini PLUSNet in Puget Sound + scouting mission off La Jolla

• PLUS - Continuing development and field work– Communications: Modem integration and HFGW – Nexgen glider (payload, buoyancy, processing, …), – Tactical sensors – add directivity and gain

• Mission management– Optimization: High currents, power, multiple gliders– Navigation and timing– Overall situational awareness

• Integrating acoustics + nav into data assimilation – mobile acoustic tomography receiver

Related Projects• ONR Philippine Sea 2009 –

Ocean acoustics deep water, QPE DRI (many)

• NASA: A Smart Sensor Web for Ocean Observation (APL, EE, JPL)

• NSF STC Coastal Margin Observation and Prediction (OHSU, OSU, UW)

• NSF ORION …

Many helped!Geoff ShillingJason GobatCraig LeeRuss LightPete SabinRex AndrewKeith van ThielKeith MagnessTroy SwansonTim McGinnisMike BoydKate StaffordSue MooreRobert MiyamotoMarc StewartJim LubyNeil BogueAndrew WhiteJim MercerLinda BuckJoe WigtonFritz Stahr and the Seaglider

Fabrication Center

Lee Freitag and Matt GrundTom Hoover, Jim Bellingham, et alJoe Curcio and the MIT kayaksClay Spikes, Dave Porter, et alYi ChaoPierre Lermusiaux

ONR sponsorship

Skip Denny and the ANTS crew

Thank you

Questions?

Backup/Extras

Glider – Kayak interactions in Monterey Bay

Kayaks pinging to glider

Graphs by Alexander Bahr

MIT Computer Science & Artificial Intelligence Laboratory

Monterey Bay MB06SG023 was allowed to drift on the surface for 2 extended periods during MB06The resulting drifts were compared to surface current predictions from the HOPS model

Leg 83

Current shear eventexperienced by glider but not captured by model

forecast nowcast

Leg 25

Temperature, salinity, conductivity data usually available within 5 min of dive completion – example SG023 dive 46

Dive 46 temperature and salinity as plotted on IOP website

recovered

Drift 2

Drift 1

78

80

SG023 surface drifts

• Dives 55 and 83 followed by surface drift tests• Data compared to current prediction models

Drift 2 shows a current shear event

MB06 Acoustic Seaglider Accomplishments

• Deploy and operate sensors in field– 428+ hours of dive time– 300+ dives (acomms, T, S, Depth, acoustics, surface currents, depth-avg

currents)• Demonstrated Seaglider communications gateway capability

– In-air – Iridium satellite – Sub-sea – acoustic modem at various depths and ranges– Passing NAFCON orders to remote kayak to prosecute target

detected/reported by other kayaks (node of LBL navigation)– Turned bottom vector sensor array node on/off

• Ambient sound– Active source emissions - Lubell source (for TL, propagation)– Marine mammals (blues, humpbacks, sea lions, …)– Ambient noise budget (ships, seismics, wind, rain, …)

• Environmental data– Temperature and salinity into Harvard and JPL models– Depth averaged and surface currents– Bottom resting mode– Adaptive sampling

Coherent processing of M-sequence coded signals

Arrival times(72.7195)

(72.282)

(72.8654)(72.9153)

(73.4143)

Peaks in each block shift due to changing s/r range

•Measured travel time changes•~3.7 ms per 27.28 s block

•Match glider kinematics•0.0204 m/s, 136 m horizontally, 33 m vertically, in 12 minutes

Relative travel time – 27.28 s

Relative travel time – 0.3 s

Relative travel time – 0.4 s