Sea Technology

MAY 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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(Top) DeSoto Canyon high-resolution bathymetry collected by the RV Okeanos Explorer. Deep-C study sites will be explored during repeated research cruises. (Right) Plumes of gas bubbles from natural seeps at Green Canyon 600 ECOGIG study site (water depth about 1,200 meters). Imaged by RV Falkor. developed the Modular Instrument Lander and Equipment Toolsled (MILET), a cost-effective alternative for deep-ocean surveys that can be deployed from the kinds of coastal ships that are most readily available for academic users. MILET is essentially a high bandwidth communication and power backbone system to a diverse set of ports on a towed, deep-sea drift platform. The fexible MILET can be used on a wide array of vessels and can carry the latest cam- 24 st / May 2013 era, sonar and sensor technology. MILET is maneuvered as the ship slowly motors along transits covering features of interest. Position in the water column, typically 2 to 4 meters above the seafoor, is controlled by fne-scale adjustment of the winch wire-out. An ultrashort baseline (USBL) transponder and Doppler velocity log (DVL) provide realtime data on location and altitude. At the heart of the MILET is a custom-made fber-optical NEXUS telemetry system comprising a MacArtney A/S (Esbjerg, Denmark) NEXUS MK C multiplexer, nicknamed the "mega mux" due to its numerous connectivity and instrumentation options. The system is interfaced with SubConn connectors, and uses a single fber-optic cable mounted on an oceanographic winch system to connect topside and subsea multiplexer units. This combination allows for fexible control and versatile application of the MILET and its onboard equipment. The fber-optic telemetry system and the winch are designed and fabricated by MacArtney. There are two modes of investigation relevant to tracking oil discharges and their aftermath. Regional surveys seek to measure diverse biological, chemical and geological phenomena to identify hydrocarbon transport pathways and habitat characteristics. Seafoor observatories, on the other hand, undertake detailed, long-term measurements of rates and processes at areas of interest. MILET has a vital role to play in both modes. It can investigate environmental gradients and special features in a site of interest, and can also be used for detailed local mapping of the seafoor and water column. Deep-C Deepwater Horizon underscored the lack of basic knowledge of the environment where the accident happened. Among the many unprecedented aspects of the blowout www.sea-technology.com

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