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MARINE & UNDERWATER SENSING
Projects:
 Coral-Based Study of Marine Environmental Metals and Regional Paleoclimate The world is undergoing a transition from an unregulated marine environment to managed oceans. Sound management of marine resources requires knowledge of the consequences of our activities. One of the CENSAM key premises is that sensor and modeling development is a key in understanding how our actions affect the marine environment. However, a useful addition to the sensor/modeling approach is historical context: how does the present state compare to what happens when there was no significant human intervention? Sensors can tell you where you are, but they can't tell you how you got there over the past century or two. Yet understanding why things are the way they are now requires an understanding of how things have changed from their natural state. Fortunately, there is a supplement available for modern observations and models: the historical record as recorded in geological archives. In particular, the Singapore region is blessed with an abundance of reefbuilding corals. These corals lay down annual density layers, and hence they can be sampled and the density layers counted like tree rings to provide a chronology that can be accurate to a few years for the past several centuries. The calcium carbonate crystals contain geochemical indicators of environmental properties such as the temperature and chemicals in the water, so geochemical analysis of dated corals can provide a history of changes in environmental properties that have occurred before the period of modern sensors. This project will begin an effort to reconstruct coral-based histories of Pb, Pb isotopes, and Cd for the marine waters of the Singapore region to evaluate the extent to which distal global-scale transport of anthropogenic contaminants and regional pollutant sources affect the environmental properties of the marine environment in the Singapore region. Our studies will involve sampling of sites that reflect regional pollutants (e.g., the eastern Indian Ocean) and local pollutants (areas near sites of heavy industrialization and agriculture).
Contact PI: Edward A. Boyle
Chemical Sensors for AUVs The main goal of this project is to develop sensors for environmental chemical monitoring capable of deployment on AUVs. An associated goal would be the implementation of underwater data networking to enable real-time data display and analysis, and permit users to control vehicles in an adaptive manner as desired. One major focus is a sensor based on mass spectrometry, for monitoring of natural waters, measuring low molecular weight hydrocarbons, metabolic gases for geochemical studies, and volatile organic compounds for pollution monitoring. The other major focus is a sensor based on laser-induced fluorescence, capable of measuring higher-molecular-weight hydrocarbons such as are common components of older oil leaks and spills, as well as biological entities such as chlorophyll, aquatic humic substances, and fluorescent tracers. In later years of the project, following the successful implementation of sensors for these several classes of chemicals, it is anticipated that the chemical knowledge obtained from the full sensor suite can be maximized using appropriate signal processing and data fusion techniques, and powerful adaptive sampling behaviors by a host AUV can also be implemented.
 NEREUS: Prototype AUV-mounted mass spectrometer  The Mystic Lake sensor network for observing methane cycling (Nepf, 2004)
Contact PI: Harold Hemond
Map-Based Navigation for Autonomous Marine Systems This project focuses autonomous monitoring and surveying the Singapore Harbor area, using surface and underwater vehicles. The system of multiple agents will be capable of individual as well as coordinated actions relative to feature maps, and adaptive sampling, and will interface with new acoustic communication and navigation systems. Further, the vehicles will host advanced sensors such as millimeter-wave radar and imaging sonar, and provide ocean deployment opportunities for sensors and other devices being developed by CENSAM colleagues. We are exploring broader opportunities in marine vehicles technology, including ultrasonic propulsion.
 Autonomous Underwater and Sea Surface Vehicles  Autonomous Navigation
Contact PI: Franz Hover
MEMS Pressure Arrays for Near-Field Flow Patterns This project will deploy inexpensive, low-power sensors, passively detecting dynamic and static pressure fields with sufficient resolution to detect objects and bodies generating the disturbance. The novel sensors consist of arrays of tens to hundreds of MEMS-based pressure micro-transducers. These sensors and processing software emulate and extend the capabilities of the lateral line in fish. The arrays will be capable of detecting near-field flow patterns and near- and far-body obstacles and vehicles, as well as mapping near-body objects. This will provide a unique capability for navigation in shallow-water and/or cluttered environments, for use with multiple AUVs, and for flow control in conventional and biomimetic vehicles.
 Lateral Line Sensing of Fish  Design of MEMS Pressure Array  Use of Passive MEMS Sensor Arrays
Contact PI: Michael Triantafyllou, George Barbastathis
Underwater Optics The goal of this project is to develop instrumentation for underwater optical imaging and spectrometry. The instruments serve a dual goal within CENSAM: (1) in-house characterization and measurement of new autonomous underwater vehicle (AUV) capabilities such as verification of the lateral line sensor operation; and (2) in-situ sensing of water properties by AUVs, including aiding navigation and hybrid acoustic/optical sensing and imaging. To serve this goal, we plan to develop novel optical instrumentation capabilities, namely (1) a high-speed holographic particle image velocimetry instrument to acquire 3D flow data from the motion of AUVs inside a water tank; (2) develop small sized optical instruments such as spectrometers for use inside AUVs; and (3) theoretically and experimentally investigate the possibility of improving visibility for optical imaging in the turbulent waters of the Singapore port.
 MIT-WHOI Aquatic Imaging Camera (Barbastathis, Millgram & Davis)  VHI: Real Time Optical Slicing & Imaging Spectroscopy
Contact PI: George Barbastathis, Michael Triantafyllou
Algorithms for Adaptive Sampling in Coastal Zone Environment; and Algorithms for Creation of Solid Models of Marine Structures This project will develop and test algorithms for planning cooperative adaptive sampling of the coastal zone ocean environment via multiple autonomous underwater vehicles (AUVs) and autonomous surface craft (ASCs). This will include measurements in all modalities available from other parts of the project via sensors mounted on these vehicles as well as on buoys and on bottom mounted instruments, and would be in association with the data assimilation, modeling and forecasting activities of the project. A second project will deal with algorithms for creation of solid models from AUV/ASC sensing systems: In the context of ship hull and near shore or harbor maritime structure inspection, we plan to develop algorithms for the creation of geometric models of underwater solid features using different sensing modalities (acoustical, vision, laser as appropriate) based on sensors mounted on autonomous surface and underwater vehicles in addition to bottom mounted sensors. Handling uncertainty will be a major component of this work.
 Time-Progressive Path Planning of AUVs for Adaptive Sampling (2-Vehicle Case)
Contact PI: Nicholas M. Patrikalakis
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© 2008 Massachusetts Institute of Technology