Glider and shipboard observations for underwater optical detection and communications

By: LCDR Alec CullenLCDR Brian Breshears

LT Ross HammererThesis Advisor: Peter C. Chu

Co-Advisor: Tetyana Margolina

Excellence Through Knowledge

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Effect of Ocean Environment on Underwater Communication and Detection

• Optical communication/detection systems are an alternative to acoustics

• The ocean optical properties are highly variable and depend on ocean environment

• Scattering by seawater and particles including chlorophyll-a causes light attenuation.

Underwater Optical Transfer Equation

http://www.whoi.edu/page.do?pid=119416&tid=3622&cid=163149

http://www.aticourses.com

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Objective

The objective of this project:

• Analyze and produce two-dimensional (2-D) maps of the glider and shipboard observed hydrographic and optical data collected by NAVOCEANO in the Arabian Gulf, Gulf of Oman, Adriatic Sea, and East Asian Marginal Seas

• Assess which basic oceanographic parameters significantly affect underwater optical transmission

• Assess spatial and temporal variations in correlation between oceanographic features and optical transmission parameters

• Obtain insight into the potential impact of optical conditions for developing optics-based naval systems in MCM or submarine/UUV communications

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The SEAGLIDER

From Applied Physics Laboratory www.apl.washington.eduFrom SEAGLIDER Fabrication Center. seaglider.washington.edu

• Profiles from surface to 1500m

• Buoyancy engine produces slight buoyancy changes to induce pitched upward or downward gliding. Internal battery pack is shifted side to side to facilitate turning.

• Uses Iridium LEO system to obtain GPS fixes, upload data, and receive command and control instructions from NAVO Glider Operations Center (GOC).

Instrumentation

1) Seabird Electronics’ SBE 41 CTD sensor• 1 Hz sample rate• T accurate to .001 degrees C• Salinity accurate to .005 PSU*• Pressure accurate to 2 dbar*

2) WET Labs, Inc ECO bb2fl optical sensor puck • Optical Backscatter @ 470nm and 650nm*• Fluorimeter: Chlorophyll-A @ 470 nm*• Samples in top 300m to preserve battery life

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Glider Data Set

Western Pacific

• 10,623 profiles from 2008-2014

• Primarily east of the Ryuku Islands

• Dynamic area encompassing portion of Kuroshio WBC

• Total area: ~ 435,000 km2Luzon

Kyushu

Okinawa

• Environmental instrumentation includes:

1. A Sea Bird model SBE CTD Measure temperature (ºC), salinity (PSU), and depth (m).

2. A Chelsea Mk II Aquatracka fluorometerMeasure chlorophyll-a fluorescence (µg/L) at wavelength 676 nanometers (nm).

3. A Sea Tech 25 cm pathlength transmissometerMeasure red light (670 nm) transmission (%).

4. APL (Applied Physics Laboratory) 1 m pathlength transmissometer

Measure blue light (490 nm) transmission (%).

Ship Board Observation -HIDEX-BP

§ A vertical profiler

§ High intake flow (up to 35L/s)

§ Long residence time

§ Faster profile rate, 200-meter HIDEX profiles takes 20 minutes to complete.

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From http://www.teamorca.org/cfiles/biolum_study.cfm

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Survey locations/Profile count

Time Survey Locations Number of Profiles

Jun 1993 Gulf of Oman 62

Jul 1993 Arabian Gulf 42

Feb 1995 Yellow Sea 58

Jan/May/Jun 1995 East China Sea 85

Mar 1996 Arabian Gulf 120

Apr 1996 Gulf of Oman 46

Apr/May 1997 East China Sea 48

Nov 1997 South China Sea 35

Mar/Apr 1998 South China Sea 54

Jul 1999 South China Sea 45

May/Jun 2000 Arabian Gulf 92

Jun 2000 Gulf of Oman 48

Sep 2000 Gulf of Oman 56

Sep 2002 Adriatic Sea 47

Jun/Jul 2001 Yellow Sea 75

Jun/Jul/Aug 2005 Philippine Sea 28

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Dataset Snapshot

• Data are binned into 1m increments.• Profiles range from 2m to 200m

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East Asian Marginal Seas profiles

• 455 total profiles spanning from 2-200m of water depth

• Cross-Correlation plots created on arbitrarily defined water masses

• Yellow Sea • Latitude 33-40N• Longitude 115-128E

• East China Sea• Latitude 24-33N• Longitude 120-130E

• Philippine Sea• Latitude 18-24N • Longitude 121-128E

• South China Sea• Latitude 12-24N• Longitude 104-121E

Cross-Correlation Values (α= 0.05)SC

S

PS

ECS

YS

10Only statistically significant values > 0.5 shownRed = + correlatedBlue = - correlated

B = Bioluminescence [Photons/L/s ] T = Temperature [ºC] S = Salinity [PSU]F = Fluorescence [µg/L] TR = T Red [%] TB = T Blue [%]

B/F B/S B/TB B/T B/TR F/TB F/TR S/F S/TB S/TR T/F T/S T/TB T/TR TR/TBFEB1995 0.570 -0.530 -0.680 -0.740 -0.800 -0.760 0.900JUN2001 -0.720 -0.850 0.560 -0.950 -0.520 0.530 0.970JUL2001 0.560 -0.940 0.960 0.590 0.960 0.590 0.970

B/F B/S B/TB B/T B/TR F/TB F/TR S/F S/TB S/TR T/F T/S T/TB T/TR TR/TBJAN1995 0.790 0.660 -0.620 0.900FEB1995 0.820 0.840 0.810 0.800 0.980 0.980 0.990 0.970 0.970 0.970MAY1995 0.540 -0.520 0.550 0.860JUN1995 0.890 0.940

B/F B/S B/TB B/T B/TR F/TB F/TR S/F S/TB S/TR T/F T/S T/TB T/TR TR/TBJun/JulAug2005

-0.570 0.950

B/F B/S B/TB B/T B/TR F/TB F/TR S/F S/TB S/TR T/F T/S T/TB T/TR TR/TBAPR1997 0.740 -0.660 0.900MAY1997 0.980 0.970NOV1997 0.150 0.660 0.540 0.650MAR1998 -0.810 -0.770 -0.700 0.660 -0.860 0.960APR1998 0.960OCT1998 0.920 0.980JUL1999 -0.640 -0.650 0.950 0.800

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Adriatic Sea Data

Dep

th(m

)

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Adriatic Sea

Arabian Gulf Data Collection

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Correlation Values in Vertical Domain

Jun 1993 AG

Jun 1993GOO

Mar1996 AG

Mar 1996 GOO

Jun 2000 AG

Jun2000 GOO

Sep 2000 AG

Sep 2000 GOO

Temp Salinity -0.73 0.76 -0.73 0.73 -0.71 0.81 -0.92 0.81Temp Biolum 0.52 0.64 0.61 0.73 0.58Temp Fluor -0.55 0.63Temp %RTr -0.68 -0.52 -0.71 -0.67Temp %BTr -0.63 -0.56 -0.72 -0.71Biolum Fluor 0.57 0.71 0.73 0.73 0.56 0.74Biolum %RTr -0.8 -0.75 -0.83 -0.5 -0.75Biolum %Btr -0.82 -0.73 -0.86 -0.54 -0.75Fluor %RTr -0.68 -0.82 -0.79 -0.85 -0.61 -0.79Fluor %Btr -0.66 -0.82 -0.77 -0.85 -0.49 -0.78

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Correlation of Derived ParametersJun 1993 AG

Jun 1993 GOO

Mar 1996 AG

Mar 1996 GOO

Jun 2000 AG

Jun 2000 GOO

Sep 2000 AG

Sep 2000 GOO

FluorPeak BiolPeak 0.61 0.79 0.74

FluorPeak Fluor50% 0.88 0.78 0.53 0.66

FluorPeak Fluor90% 0.8

FluorPeak Biol50% 0.69 0.87 0.57 0.95

FluorPeak Biol90% 0.69 0.68

FluorPeak RedBApeak 0.78 0.63

FluorPeak BlueBApeak 0.79 0.65

FluorPeak EZD 0.69 0.53 0.72

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Future Work

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• Glider data analysis– 10,000+ profiles over a 6 year period– Different optical sensor

• Ability to get scaling value from backscatter (Glider) to transmission (HIDEX)

• High resolution classified data analysis– Global data set enroute from NAVOCEANO

Thesis Plans

• “Effects of Varying Oceanographic Conditions in the Arabian Gulf on Underwater Optical Communications and Detection” by LT Ross Hammerer, Mar 2016

• “Effects of Varying Oceanographic Conditions in the Adriatic Sea on Underwater Optical Communications and Detection” by LCDR Alec Cullen, June 2016

• “Effects of Varying Oceanographic Conditions in the East Asian Marginal Seas on Underwater Optical Communications and Detection” by LCDR Brian Breshears, June 2016

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Excellence Through Knowledge

Questions?