The Martha’s Vineyard Coastal Observatory
James Edson, Thomas Austin, Wade McGillis, Mike Purcell, Robert Petitt, Jonathan Ware, Marguerite McElroy,
Sheila Hurst, and Carlton Grant
jedson@whoi.edu, taustin@whoi.edu, wmcgillis@whoi.edu
Woods Hole Oceanographic Institution, Woods Hole, MA, USA

Abstract. Underwater observatories with real time data andvirtually unlimited power transmission capabilities (whencompared to traditional oceanographic moorings) are
beginning to provide scientists with continuous access to thecoastal and even open ocean.
The Woods Hole
Oceanographic Institution (WHOI) is committed to efforts
that are providing this technology to scientists, students, andthe general public. As part of these efforts, WHOI isconstructing the Martha’s Vineyard Coastal Observatory on
the south shore of the island in the coastal waters of theAtlantic Ocean. This paper describes the new facility, andin particular its system architecture, as developed by WHOI
with support from the National Science Foundation.

transportation, researchers have easy access to theunprotected southward facing shore of Martha’s Vineyard,
allowing nearshore processes to be investigated locally.

1. Introduction
Coastal processes are of crucial societal importance.
Engineers and planners long have been concerned withcoastal protection, particularly in heavily populated areas
where wave attack, set-up, and shoreline erosion threaten
coastal structures. Geologists have been struggling tounderstand how the astonishing variety of coastal geologicalfeatures form and evolve in response to nearshore
processes. Coastal meteorologists are only now beginning
to investigate physical processes that are unique to thecoastal environment, including the adjustment of the nearsurface flow to extreme changes in the surface roughness,differential heating, and extensive sea-spray production in
the surf zone.
WHOI scientists and their colleagues have been
involved in coastal and nearshore field studies ranging froman investigation of respiratory irritations caused by airborne
sea-spray generated during outbreaks of red-tide(Woodcock, 1948) to more recent investigations of the flow
structure measured in the atmospheric (Mahrt et al., 1998)
and bottom boundary layers (Lentz and Trowbridge, 1991),
waves in the shoaling (Elgar and Guza, 1985), surf (Chen etal., 1997), and swash (Raubenheimer et al., 1995) zones,
and nearshore morphological changes at scales ranging
from sand bars (Gallagher et al., 1998) to orbital ripples(Traykovski et al., 1999). To date, none of these studies
have taken advantage of Cape Cod and the Islands’
southward facing Atlantic coastline because Martha’s
Vineyard and the Elizabeth Islands protect the shorelinefrom ocean waves, and thus preclude investigation ofwave-driven nearshore and surf zone processes. In contrast,
using both coastal research vessels and groundFigure 1. Cable routes for the MVCO. The solid line
indicates the present cable. The dotted lines indicate thecable that will be deployed in the near future.
The approximately 25-km long southern shoreline ofMartha’s Vineyard is nearly straight with homogeneousalongshore bathymetry upwind of the predominantly
southwesterly winds from the open ocean. Waves andcurrents cause sediment transport and beach erosion that
results in an average of 2-3 m of shoreline retreat each year.
The orientation of the shoreline allows the effects of winds,
waves, and currents in mild and severe conditions to beobserved, and thus provides a natural laboratory to study
nearshore hydrodynamics, sediment transport, biologicaland benthic processes, gas transfer, aerosol physics, andcoastal meteorology.
To take advantage of this shoreline and its research
opportunities, WHOI is building the Martha’s Vineyard
Coastal Observatory (MVCO) near South Beach in
Edgartown (Edson et al., 2000). The MVCO is nearing
completion and is expected to be operational by the summer

Figure 2. Schematic showing the various components of the MVCO. Instruments at the shore lab and on themeteorological mast are operational. The offshore node will be operational by the summer of 2001.
of 2001. The project was initiated by scientists in the
Coastal and Ocean Fluid Dynamics Laboratory (COFDL) at
WHOI, who will use the observatory to monitor coastal
atmospheric and oceanic processes. Specifically, theobservatory is expected to:
•
•
•
•
•
•

Provide a local climatology for intensive, short duration
field campaigns.
Further facilitate regional studies of coastal processes
by providing infrastructure that supports easy access topower and data.
Provide a reliable system and rugged sensors that allow
opportunistic sampling of extreme events.
Provide continuous long term observations for climate
studies.
Provide a means for public outreach and educational
programs.
Provide a component of a larger network ofobservatories and platforms for real-time observations
and initial conditions for ocean and atmosphericmodels.

The MVCO includes a small shore lab located 1.5 km
inland, a 10-m meteorological mast 50-m from theshoreline, and a subsurface node mounted on the bottom in
12-m water depth, 1.5 km offshore as shown in Figure 1.
The meteorological and subsea instrumentation is connected
directly to the shore lab via an embedded electro-opticpower cable.
The core set of instruments at themeteorological mast will measure wind speed and direction,
temperature, humidity, precipitation, CO2, solar and IR
radiation, and momentum, heat, and moisture fluxes. The
core oceanographic sensors at the offshore node willmeasure current profiles, waves, temperature, salinity,
turbidity, fluorescence, CO2, dissolved oxygen, and bottom
stress.
Besides the core set of instruments, the offshore nodeand the meteorological mast will act as "extension cords"
into the coastal environment because they will allow
connection of a wide range of instruments for prolonged
deployments. The node architecture is designed to allow
simple integration of any sensor by the implementation of astandard guest port configuration. Each guest port will
provide a flexible DC power interface and a choice of datainterfaces, including Ethernet, RS-232, and RS-422
communication options. The observatory will be connectedto the WHOI network via a high-speed network
communications link.
A web-based, graphical userinterface provides the user with total control over his
assigned port, allowing him to power on and off his sensor
system at will, and continuously monitor its status fromanywhere in the world.
The system is designed to be expandable, with spare
power and fiber-optic connections provided for these futurenodes. For example, two other offshore nodes are planned
for the near future; a nearshore node just outside the surfzone at 6-7 meters depth and another located 5 km fromshore at 20 meters depth as shown in Figures 1 and 2. The

latter node will provide power and data access to
instruments deployed on an air-sea interaction tower thatwill span the coupled boundary layers from the ocean
bottom to a height of 10-m above the sea surface.

2. Overall Description
The MVCO is located along the southern coast of
Martha's Vineyard. This coastline is characterized by a 25
km long, south-facing beach, which provides ideal exposurefor the predominant winds from the southwest. It is also
routinely exposed to severe coastal storms during the wintermonths that are of particular interest to the scientists
involved in this project. Therefore, the MVCO will provide
a unique setting on the East coast to investigate coastal
processes that will complement the research being
conducted at the existing observatories along the easternseaboard shown in Figure 3.

meter mast extending above the laboratory holds sensors tomeasure solar and infrared radiation, rainfall rate, temperature,humidity, wind speed and direction. We currently plan toconnect the shore laboratory to WHOI via a wireless 11 Mbps
data link with a 56 Kbps leased-line as back-up. The laboratory
includes an automatic backup power generator to continue
operation of the entire system during power outages. All
computer and equipment operation will be monitored remotelyfrom WHOI.
2.2 Cable Description and Installation
The main cable design consists of six AWG13 copper
power conductors, with high voltage insulation. Ten singlemode optical fibers are contained in a loose-tube assemblyat the center of the cable. The core is jacketed with apolyurethane sheath, and is protected by two layers ofcross-laid armor and a polyethylene outer jacket. The cablehas a maximum working load of 1,573 Newtons, which iswell above the anticipated loading experienced during thecable installation process.

GoMOOSMVCO

Shore
Station
CBOS

Figure 3. Some of the coastal observatories and observing
systems along the northeastern seaboard (yellow stars).
Also shown are the existing NDBC buoys (red diamonds)
and CMAN stations (green triangles).

2.1 Shore Laboratory
WHOI has leased space at the publicly owned Katama Air
Park, which is a grass strip airfield located in Edgartown, MA,
and has constructed a small, unmanned shore laboratory at thesite. The airfield provides a safe, secure location for the shorebased laboratory with proximity to power andtelecommunication services. The shore laboratory is thetermination point for the fiber-optic/power cable. It contains thecomputer systems and power supplies necessary for controllingthe sensors and logging the data locally via these cables. A 10-

Met Mast
To NodesFigure 4. The various techniques used in cable burial:
White – traditional trenching, Yellow- directional drilling,
Green – jetted trench.
The cable was buried from the shore lab to the planeparking area using traditional techniques along the airfieldrunway. The route is indicated by the white line in Figure
4. WHOI then utilized directional drilling technology tocross the beach area with the least environmental impact.
The drilling operation, accomplished in May, 2000,

provided a sleeved hole, 626 meters in length, between theairfield and the seafloor (to approximately 300 meters off ofthe beach). A second hole (206 meters in length) was
drilled to provide a cableway to the meteorological sensor
mast, located on the beachfront. These pathways are givenby the yellow lines in Figure 4.
The seafloor cable has been buried approximately 1 to
1.5 meter below the seabed, from the offshore end of thedrilled section (i.e., the green arrow in Figure 4) to thelocation of the offshore node. The cable was buried using atechnique that relied on high pressure water jets that createda trench for the cable to fall into as the operation moved
along the cable route. As shown in Figure 1, the cable route
was chosen to place the offshore node closer to the center ofthe island’s coastline. This positions the sensors in simpler
bathymetry at a location that is upwind of themeteorological sensors for southwesterly winds.
2.3 Seafloor Node
The MVCO will initially include one seafloor node,with two more planned for the near future. The seafloor
node will be constructed on a pedestal base that ispermanently jetted into the seabed at the offshore site. The
pedestal will support the instrument frame at a distance ofapproximately 0.5 meters above the bottom, in order toallow sand to flow through without accumulating within theframe. The node will contain twenty “guest ports” which
will be available to the users via a simple, 8 pin underwater
matable connector.
Each port provides electricalconnections for two isolated DC power supplies (12V and
24V) and a remotely programmable data interface allowing
Ethernet, RS-232, or RS-422 connections. The seafloor
nodes will be equipped with a core set of sensors including
an Acoustic Doppler Current Profiler, Acoustic Doppler
Velocimeters, an altimeter, and oceanographic sensors tomonitor a wide range of water properties including
temperature, salinity, turbidity, and dissolved gases.

Figure 5. MVCO seafloor node.
Figure 5 shows the layout of the offshore seafloor node.
The electronics housing contains all the power andtelemetry circuits. The guest port connectors will be easily
accessible by divers. The neutrally buoyant instrument
frame, which will be the upper section of the node, will beeasily recovered for routine maintenance and upgrades. The
lower frame houses an oil-filled transformer box. The
transformer box contains three step-down transformers.
Diver matable fiber-optic connectors mounted on thetransformer box provide access to the main cable’s opticalfibers. When the upper instrument frame is recovered,divers detach the fiber-optic and power connectors, leaving
the transformer box on the pedestal.
2.4 Meteorological Sensor Mast
A meteorological sensor mast (10 meters tall) is
located near the beachfront, just behind the present locationof the dunes. The mast rises approximately 8 meters above
the dunes and 13 meters above mean sea level. This heightplaces the sensors above most of the flow distortion inducedby the changing bathymetry (Jensen and Peterson, 1978).
Investigations will be conducted to quantify and remove theremaining effects of flow distortion that are present at thesensor locations atop the mast.
The mast has a core set of fast response sensors that
include a 3-axis ultra-sonic anemometer, which also
provides fast-response temperature measurements derived
from its sound speed measurements, and an infrared
hygrometer/CO2 sensor. Additional sensors will measure
the mean wind speed and direction, relative humidity,
temperature, pressure, and CO2 levels in the atmosphere.
The fast response sensors will measure the exchange ofmomentum, heat, and mass between the atmosphere andocean when winds are onshore. The mast also includes anumber of extra guest ports that will be available forgeneral use.

3. Power System
There are six AWG13 power conductors in the seafloor
cable, with insulation ratings of 2500V.
These six
conductors provide for three independent power circuits
offshore. Initially, only one of the three circuits will beutilized for power to the seafloor node. The other two
circuits will be reserved for the future offshore nodes. Eachcircuit will be capable of providing 4 kW of power to a
distance of up to 5 km from shore. Power will betransmitted from shore at 1,500 Vrms, using single phase
60Hz AC.
Power is derived from the local utility, with generator
backup and a Uninterruptible Power Source (UPS) to
maintain seamless power transfer during local outages. The
automatic generator/UPS combination will maintain datacollection capability even during severe storm events. At
the seafloor node, the high-voltage AC will be stepped
down to 240VAC using a transformer.
This 240VAC
supply will be fed into the main electronics bottle where it
will be converted to regulated DC power at each guest portinterface using internal AC/DC converters.
These
converters supply isolated 12VDC and 24VDC power at up
to 100 watts at each of the guest ports.

Power supply isolation will be maintained between
ports, allowing for independent ground fault sensing of each
port. Each guest port will be monitored and controlled by alocal Motorola 68HC11 microcontroller. This controller
can connect or disconnect the AC input for that port, andcan power on or off the two DC outputs as well. In
addition, it monitors voltage, current and ground fault status
for both the 12 VDC and the 24 VDC power supply outputs.
The port will be configured to automatically shut down
power to a guest port in the event that a fault is detected,
and thus prevent further damage.

4. Networked Data Telemetry
The seafloor node electronics and the met mast data
telemetry electronics are essentially identical. Each site will
be connected to the shore laboratory by a 1 Gigabit/sec
Ethernet fiber-optic trunk line with AC power. A Cisco
Systems Ethernet switch provides 24 10/100 BaseT
Network connections at the nodes. The same Ethernet
switch will be used at the shore laboratory. Each switch
contains a single-mode fiber-optic networking module aswell as the 24 RJ-45 twisted pair connectors. The buried
fiber-optic cables will be connected directly to the Cisco
Ethernet switch to transmit the networked data at 1 Gbps toand from the shore laboratory.
Because all of the sensor nodes will be network
connections, all nodes will be connected together on acommon Ethernet network inside the shore laboratory at the
Katama Airpark. This network will be connected to theglobal Internet in two ways. To provide the highest
possible bandwidth to users working locally at WHOI, a
direct connection to the WHOI campus network is desired.
Currently, an 11 Mbps spread spectrum radio link isplanned as the primary communication link between the
shore laboratory and WHOI. A 56 Kbps leased line has
been installed for use as a preliminary communication link,
and will serve as the back-up to the radio link, when it isinstalled.
We expect that many of the scientific instruments
connected to the guest port will initially utilize
asynchronous serial communication interfaces such as RS232 to control the instruments and collect data. Therefore, amethod was needed to integrate multiple serial ports into the
Ethernet data system. This function will be provided by a
Cisco Systems serial communications server, which
supplies 16 serial ports for distribution among the various
user ports. The communications server has an Ethernet
interface that connects to one of the network ports on the
Ethernet switch. It allows direct IP, telnet, or COM-port
redirection access to any of its serial ports, thus allowing
users to access their underwater instrument from anywhereon the Internet.

5. Guest Port Interface
At each node there will be a number of identical guest
ports. The main seafloor node will support 20 ports, and 10
ports will be provided at the met-mast. Each port is
assigned an 8-pin underwater matable connector as shownin Table 1.

The data lines will be remotely programmable for one ofthree interfaces: 10/100BaseT Ethernet, RS-232, or RS-422.
Baud rates up to 115 kbps will be supported on the serialinterfaces. The data common (RS-232 and RS-422 only) isconnected to the 12V Common pin. The Ethernet interface isconnected to the Ethernet switch, which in turn routes all data
traffic over the fiber optic cable to the shore lab, where it will berouted to WHOI and the World Wide Web.
If the user elects to use RS-232 or RS-422, these serial
ports will be accessible via the Ethernet using TELNET,
custom software (direct IP), or commercial COM-Portredirection software, the latter of which WHOI will provide
to the users. The COM-Port redirection software allows
users to run existing applications that normally connect to a
local COM-Port. The software automatically redirects thetransmitted and received messages to and from the remote
port, over the Ethernet. For low-speed serial ports this will
even work across the Internet. However, we expect thatmost users will store data locally and access this data
remotely.
Table 1. Pin Assignments for the Guest Ports
Pin 1

12V + (100 Watts max)

Pin 2

12V Common (Data Common)

Pin 3

24V + (100 Watts max)

Pin 4

24V Common

Pin 5

Data TX+

Pin 6

Data TX-

Pin 7

Data RX+Pin 8

Data RX-6. Conclusions
The Martha’s Vineyard Coastal Observatory iscurrently being installed off of the south coast of the island
to monitor coastal atmospheric and sub-sea conditions.
This observatory will provide scientists with direct access tothe coastal environment and allow continuous
measurements of environmental parameters under all
conditions, including the severe storms of the North
Atlantic. The observatory has been designed to be inoperation for a minimum of 25 years, with minimal
maintenance. Generic user guest ports provide simple
connection of all types of instrumentation using
conventional power and data interfaces. Spare power
conductors and optical fibers in the main cable provide forsignificant expansion capability for future offshore nodes,
AUV docking stations, and special experiments.
Acknowledgements. The authors would like to thank the
Town of Edgartown, MA for their support throughout thepermitting and installation phases of this project. We would
also like to thank Steve Elgar, Britt Raubenheimer and Peter
Traykovski for their review of part of this manuscript. This
work was supported by the National Science Foundation

(NSF grant OCE-9871120)
Oceanographic Institution.

and

the

Woods

Hole

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