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SandyDuck '97 Facts and Instrument Descriptions
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Interesting Facts

Participants: over 250
Organizations: 26 total, 22 US, 3 Canadian, 1 United Kingdom
Sponsors: US Army Corps of Engineers, Office of Naval Research, US Geological Survey
Sensors: over 400
Cables: 150 cables installed to connect sensors to the shore stations
Computers: 115 computers to collect, exchange and process data.
Portable Trailers 12
Different Investigations 30 (though they vary widely in size and complexity)
Years in Planning 7

SandyDuck '97 Schedule

15 June - 21 September 1997: Deployment of Instruments
22 September - 31 October 1997 Experiment
November 1997 Instrument removal

Instruments

During SandyDuck, state-of-the-art instruments and technologies will be used to make measurements of the coastal environment under all conditions. Some of the unique instruments being used include:

Fiber Optic Backscatter Sensors (FOBS)- A major problem with most instruments that measure sediment movement is that the physical size of the sensor is much larger than sand grains. The innovative FOBS solves this problem by using small optical fibers and light to measure the movement of individual sand grains.

Acoustic Instruments - a whole range of new oceanographic instruments are using underwater acoustics to make new or better observations. Some of the acoustic instruments being used are:

  • Acoustic Altimeters - In the past, our knowledge of how much the beach eroded was gained by comparing maps of the nearshore zone collected before and after a storm. Although this provides a measure of the amount of sand eroded from the beach and deposited offshore, it doesn't provide any information on how the sand actually moved. During SandyDuck acoustic altimeters (sonars) will be deployed in shore-perpendicular and shore-parallel lines. Each sonar will continuously record the changing height of the bottom under it and collectively they will provide accurate maps of ocean bottom as it changes. In one investigation a line of altimeters placed very close together (called a Multiple Transducer Array) will be used to make fine-scale measurements of the movement of ripples on the seafloor.
  • Current meters - Unlike most current meters which interfere somewhat with the water flow by their very presence, acoustic current meters use sound to measure the water movement some distance away. This improvement helps collect better and more accurate current measurements.
  • Side-scan Sonars - Like the one used to locate the Titanic, Side-scan sonars of various types will be used to literally use sound to paint pictures of the ocean bottom as it changes. Of particular interest are the development and movement of "megaripples", large ripples in the sediment that appear to be of great importance in the movement of sediment. Small side-scan sonars will be permanently placed underwater and used to observe megaripples as they move around. A larger system will be mounted on the CRAB and used to provide an overall map of where the megaripples are.
  • Secscan Sonars - This sonar is capable of looking sideways through the water and measuring the currents. Two of these sonar devices will be installed offshore in 6.5 m (20 ft) water depth in such a way as to develop a map of the currents in a 200x500 m (650x1600 ft) region close to the shore. These measurements will complement the point measurement of the other current meters and should provide some of the most detailed observations of rip currents ever collected.
  • Acoustic Concentration Profiler - Like the acoustic current meters, the Acoustic Concentration Profiler is able to measure without intruding into the flow. It detects the amount of sediment being moved and can also provide a measure of how the concentration of sediment varies with height above the bottom.

Video Cameras - Nearly every wave passing through the SandyDuck experiment will be recorded by video cameras located on special towers. Although video cameras are no in themselves unique, by cleverly processing the collected images, SandyDuck scientists will be able to map the ocean bottom, measure surface currents, measure waves, and identify important motions in the coastal ocean that are difficult to observe with the naked eye, or measure with conventional instruments.

Radars - The same type of radar systems used to locate ships at sea can also be tuned to make measurements of waves and currents and to remotely sense the underlying shape of the nearshore bottom. Several marine radars will be used to complement the point measurements of the other instruments. In a completely different application, Ground Penetrating Radar will be used to map out the geologic structure of the beach.

Pressure Sensors - Pressure sensors placed underwater measure the weight of the water above and are used to measure waves and water levels. Many pressure sensors will be installed in different configurations called arrays. Three large arrays of pressure sensors and several smaller ones will be used to obtain detailed information about the waves, including their direction of approach to the shore. Pressure sensors will also be used to provide a precise measure of the water level close to shore, useful in measuring the storm surges associated with hurricanes and passing nor'easters.

Hydrophones - Hydrophones are underwater microphones which will be used to listen to wave breaking and to measure the natural sounds in the ocean. These will also be installed in multiple hydrophone arrays.

Electromagnetic current meters (EMCM)- Though not as elegant as the newer non-invasive acoustic current meters, the electromagnetic current meter has long been the workhorse of oceanographers trying to measure nearshore currents. These current meters work on the principle that a conductor (the water) flowing through a magnetic field (generated by the current meter probe) produces a voltage proportional to its velocity. Numerous EMCM will be deployed as part of multi-instrument packages.


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