Limitations to LongTerm Deployment of Sensors in the Ocean

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Limitations to Long-Term Deployment of Sensors in
the Ocean or How to build a cabled biogeochemical
observatory to survive in the Southern Ocean
Issues Science requirements Communications Power
Biofouling Corrosion Maintaining Accuracy the
need for auto-calibration Failure points
underwater electro-optical connectors EOM
cable Deployment and Maintenance
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A Variety of Deployment Platforms to Make
Measurements over Extensive Spatial and Temporal
Scales

• Power
• Communications
• Data storage

Most constrained
Least constrained
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Polar Remote Interactive Marine Observatory
(PRIMO)
Location 3 km west of Palmer Station,
Antarctica Depth 100m Power and
Communications 0.68 EOM cable, 1 Kw Full-time
100 BT Ethernet
Lifetime 25 years with annual maintenance Initial
Cost lt 2 million Controllability real-time
resource allocation Flexibility expandable,
upgradeable Reliability redundancy in major
systems, remote control of each sensor or
subsystem
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What do we need to measure?
Southern Ocean Food Web
Physical Temperature, Salinity- SBE 49 CTD Water
currents- RDI ADCP Turbulence- MAVs Intrinsic
Optical Properties- WET Labs ECO
puck Irradiance- Satlantic
Chemical Nitrate- ISUS Iron- Subchem Dissolved
organics- CDOM O2 Aanderaa optode CO2- SAMI
pCO2
Biological Phytoplankton- chlorophyll
fluorometer Zooplankton- Video Plankton Recorder,
acoustics Fish- Imagenix sonar, video PTZ
camera Seals- sonar, video PTZ camera Whales-
sonar, hydrophone Birds- video PTZ camera?
Engineering Power Fault detection Roll, pitch,
yaw Proximity to ice Winch status
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Polar Remote Interactive Marine Observatory
(PRIMO)
Palmer Station 100 m depth May 2006
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• Real-time web site
• http//4dgeo.whoi.edu/vpr
• Deployment location
• Data display
• tabular data
• plankton images
• time series plots
• Plankton key
• Interactive control
• Data file download

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Mass Bay Oct-Nov 2002
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Mass Bay Oct-Nov 2002
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Mass Bay Oct-Nov 2002
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AUV/Gliders
Cabled Observatories
The Vision
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Biofouling- the attachment of organisms to
surfaces in contact with water Issues Surface
hydrodynamics- cables, vehicles Heat exchange-
sensors Optical performance- sensors Mechanical
performance- inhibit release mechanisms Galvanic
corrosion, electrolysis- compromise
seals Additional mass- buoyancy failure
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• Typical anti-fouling agents/approaches
• Organo tin compounds (3 mo- 1 y)
• TBTO (phased out by 2007)
• 1020A-Navy formulation
• Alum-A-Tox
• No Foul
• OMP-1-8
• Copper based paint (3 mo 1 y)
• slow release
• ablative
• Oxidizers (y)
• Chlorine
• Bromine
• Alconox
• Cayenne pepper in silicone grease (mo)
• Electrochemical control (y)
• Mechanical wipers
• Copper shutters (mo- y)

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• New directions
• Non-toxic surface modifiers
• (hydrophilic and hydrophobic)
• Silicones, fluoropolymers, ethyl vinyl
  acetates
• Pulsed Plasma laser irradiation
• UV irradiation- e.g., VPR strobe light
• Sponge extract (Kelly et al. 2003)

Xenon strobe
nanometers
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CMO 13 m TBT Porous plastic rings in intake
lines ac-9 Absorption coefficient at 412, 510,
676 nm
biofouling
fluorometer Chlorophyll-a
HyCODE Copper tubing in intake
lines ac-9 Absorption coefficient at 412, 510,
676 nm
Phytoplankton bloom
No fouling
fluorometer Chlorophyll-a
Manov, Chang and Dickey, 2004
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Manov, Chang and Dickey, 2004
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WET labs, Inc copper shuttered ECO fluorometer
and ECO-VSF sensors
Ocean Physics Laboratory Shuttered radiometer
Following 5 month deployment at the Bermuda
Testbed Mooring
410-day time series of non-biofouled
chlorophyll-a and downwelling irradience at 555
nm Sea of Japan Sep 2001-Oct 2002
Manov, Chang and Dickey, 2004
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Aanderaa Optode after 7 month deployment on the
AVPPO at MVCO
5 day record of Oxygen profiles at end of 7 month
deployment
Copper ring not shown
Oxygen (µM)
Single profile
Time (s)
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MVCO Inshore node and pedestal
Flow Cytobot intake with copper screen after 4
mo R Olson
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Failure points underwater electro-optical
connectors Galvanic corrosion EOM
cable mechanical winch
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EO plunger underwater pluggable relatively
reliable with proper handling
Glass re-enforced epoxy with o ring seals.
Sensitive to vibration (water flow) difficult to
seal, face is easy to chip.
Glass re-enforced Epoxy Bulkhead with molded
rubber boot. Economical, dry mate only, prone to
leakage due to vibration or improper lubricating
Wet mate connectors, Gold pins molded into
neoprene. new to the market, expensive, no known
failures, less prone to improper mating and flow
vibrations causing leaks, good at low temperatures
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FIBER OPTICS at the MVCO
Subconn Optolink multi-fiber, dry mate only.
1000 mating cycles Cost 3-8,000 depending on
configuration Reliability excellent
ODI Hybrid multi-fiber, multi-conductor with
roller seals for underwater plug ability. 100
mating cycles before refurbish reqd. Cost
35,000 Reliability under testing
DG OBrien single fiber connector Corrodes on wet
pulg able gland 15 mating cycles Cost 3,000
aluminum
titanium
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Metal or Alloy
Galvanic voltage (mv)
Least Noble
aluminum
General Rule lt200 mv between materials
Stainless steel
Galvanic corrosion due to aluminum housing and
stainless steel clamps
Zinc anode
Exposed o-ring
Most Noble
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Maintaining Accuracy auto and remote calibration
Developing methods for introducing external
standards
Sea Bird CTD ISUS- nitrate SubChem- nitrate,
iron, phosphate Aanderaa O2 SAMI-CO2
Example of continuous auto calibration VPR- 256
frame running mean with background subtraction
sample frequency Target sensor
processor absolute level
gradients calibration
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Operation of an Autonomous Winch
Traction head must maintain constant torque on
drum
Sediment in traction head caused failure at MVCO
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• Recommendations
• to mitigate negative effects of long-term
  deployments
• Sensors should share common resources to
  facilitate anti-fouling
• e.g., pumped CTD, fluorometer, transmissometer
• Develop external calibration standards that can
  be implemented remotely
• and/or automatically
• Use high quality, tested connectors even if they
  are pricey
• Be extremely careful of mixing unlike metals
• KISS- complicated approaches usually fail
• Establish more test-beds under a variety of
  conditions
• Coastal, deep sea, hydrothermal vents, ice
  covered, freshwater,
• Establish dedicated instrumentation facilities

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Microbial Sensors
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Optical Imaging Sensors
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The Autonomous Vertically Profiling Plankton
Observatory (AVPPO)

• Autonomous Operation battery with Irridium
  communications
• Cabled Operation shore power with ethernet over
  fiber optic communications
• Sensors on board
• Plankton and Marine Snow
• Video Plankton Recorder (60 Hz)
• Bio-Optical (1-10 Hz)
• Wetlabs ac-9
• Satlantic radiometers - 412 to 683 nm.
• Fluorometers Chlor, CDOM
• Environmental (1-20 Hz)
• CTD
• u, v, w, _at_ 20 Hz (MAVS)
• pO2 (Aanderaa), ISUS-nitrate
• Engineering (1-50 Hz) roll, pitch, yaw