The Extended Draft Platform: A deep-ocean observatory

The tri-moored Extended Draft Platform (EDP) is designed with industry and NSF support to provide substantial power and bandwidth to the seafloor and a stable surface platform for instruments and communications. Originally planned for multi-year deployment at a mid-Atlantic site for multipurpose measurements (swell, meteorology, aerosols, seismology, ocean basin heat content, and detailed ocean structure), the prototype will first be tested in Malaysian waters. This deployment will generate early science results and provide a testbed for power generation, platform performance, communications, and sensor technologies. The EDP comprises three vertical columns between a triangular deck structure and a submerged pontoon. The columns and pontoon are raised when at quayside and during towing. When lowered, the structure behaves like a deep draft semi-submersible and motions are comparable to those of a spar buoy. The EDP will have a draft of about 23 m and the deck will be over 10 m above the sea surface. It will weigh 800 t and be able to support payloads of over 50 t. An offshore supply vessel assisted by a small offshore tug can install the EDP while an ROV equipped vessel would install the electro-optic (EO) cable and the seafloor instrumentation. It is designed to generate 10 kW of power on the platform and deliver 500 W to seafloor instruments through the EO cable. Substantial communications bandwidth will be provided by C-Band satellite telemetry for delivering all data collected in near-real-time with latencies of seconds.