M. Chaffey

Communications and power to the seafloor: MBARI's Ocean Observing System mooring concept

Operating instrumentation for collecting time-series experimental data from remote benthic sites in the worlds oceans has long been a challenging problem for oceanographers. A moored buoy system concept is presented that provides bi-directional near real-time communication to remote benthic instrumentation at flexible sites up to 4000 m deep using an electro-optical anchor cable. Designed to be deployed from regional class vessels, the mooring system is to be one of the main platforms for the MBARI Ocean Observatory System (MOOS) currently under development. The system concept supports a broad range of instrumentation and sampling strategies including benthic instrument clusters covering up to 10 km of seafloor, upper water column instrumentation and future AUV docking operations. Described are the functional requirements of the mooring system, the design approach, the results of the design trade-off studies completed and the resulting mooring concept design.

MBARI's buoy based seafloor observatory design

There has been considerable discussion and planning in the oceanographic community toward the installation of long-term seafloor sites for scientific observation in the deep ocean. The Monterey Bay Aquarium Research Institute (MBARI) has designed a portable mooring system for deep ocean deployment that provides data and power connections to both seafloor and ocean surface instruments. The surface mooring collects solar and wind energy for powering instruments and transmits data to shore-side researchers using a satellite communications modem. A specialty anchor cable connects the surface mooring to a network of benthic instrumentation, providing the required data and power transfer. Design details and results of laboratory and field testing of the completed portions of the observatory system are described

Dynamic modeling and actual performance of the MOOS test mooring

This paper presents a comparison between model predictions made with WHOI-Cable and actual measurements of the tensions in a deep-water oceanographic mooring. The mooring is part of the MBARI Ocean Observing System (MOOS) that utilizes an electro-optical-mechanical (EOM) cable to deliver power and communications to a sub-sea network of instruments. The predictions agree acceptably with the measured results, and improvements to the model and validation system that will be incorporated in the next deployment are discussed. Also presented is an outline of the information learned about the mooring cables service environment, both from the deployment results themselves and from the cable dynamics model.

Distributed data and computing system on an ROV designed for ocean science

MBARI is currently developing an electrically propelled remotely operated vehicle (ROV) designed to carry science payloads to 4000 meters ocean depth. Mission requirements for accurate navigation, precision maneuvering and extensive sensor capabilities place large demands on the data gathering and control system. The ROV must operate reliably in an extremely hostile ocean environment while retaining enough flexibility to support varied scientific missions for a decade or more. An ROV system architecture has been implemented that incorporates Hewlett Packard UNIX workstations, shipboard and vehicle mounted VMEbus and microcontroller based computers all linked to form a distributed data gathering and control network. In-water tests of the ROV have shown that a distributed, multiple processor system shows promise as a practical solution for interfacing the large number of sensors and actuators on a research ROV and provides considerable system adaptability.<<ETX>>

The use of snubbers as strain limiters in ocean moorings

Buoy based seafloor observatories require lightweight synthetic strength member electro-optical anchor cables to be feasible. Typically these cables have maximum elongations of around 0.6% before damage occurs to the copper and optical elements and therefore provide minimal compliance to absorb wave and current forces acting on the surface buoy and cable. A stretchy mechanical system known as a snubber has been developed at WHOI for absorbing wave energy and protecting the buoy electro-optical cable from excessive strain. Results are presented from field trials of three different ocean mooring designs that all use snubber hoses as a key design element.

DEEPWATER MOORING DESIGNS FOR OCEAN OBSERVATORY SCIENCE

This paper describes the current state-of-the-art in mooring systems appropriate to the deepwater ocean observatory context. The technological challenges that need to be addressed in order to realize moored ocean observatories as envisioned for the next generation of ocean observing systems are outlined.

Establishing a Benthic Cabled Observatory with ROV Based Cable Deployment

The Monterey Bay Aquarium Research Institute (MBARI) in support of the MBARI Ocean Observation System (MOOS) Science Experiment 2006 (MSE06) has established a benthic cabled observatory. The goal of MSB 06 is to study deep seafloor processes within and adjacent to the outer Monterey Bay Submarine Canyon. At the study site near Shepard Meander, a Benthic Instrument Node (BIN) and a McLane Vertical Profiler have been deployed in the axial channel of the canyon at depths of 3,450 meters. On the adjacent flank, outside the canyon another BIN has been deployed at a depth of 3,000 meters. These interdisciplinary BINs and profiler will be interconnected with a fiber optic/power cable using the ROV Tiburon. This will establish a network that can measure currents, suspended sediments concentrations, salinity, and temperature at these sites. The BINS and profiler will be cabled to a MOOS mooring. A satellite link from the mooring to shore will be used to monitor system function as well as deep sea conditions during the experiment. The ROV based cable deployments will consist of 3.5 kilometers between the lower and upper BINs, 2.5 kilometers between the upper BIN and the MOOS mooring and 200 meters between the profiler and lower BIN. Borrowing from the cable laying tool sled technology developed for the ROV Ventana (Bird 2002), this effort will integrate the knowledge gleaned from the Canyon Dynamics experience to the ROV Tiburon and MSE06. Some of the challenges involved in this project include weight constraints, power requirements, cable management, navigation, and electro/mechanical controls. In the future this technology will actively support the (Monterey Accessible Research System (MARS), and ORION/OOI. This presentation will deal specifically with the cable laying tool sled developed for the ROV Tiburon, cable packs, and infrastructure created to accomplish these tasks. Elements include the cable laying tool sled, BIN platforms, interconnects, profiler, mooring bottom expression, and cable handling equipment. Design elements includes; integration with the ROV Tiburon, meet operational weight constraints, the ability to (pick up, drop, and reacquire the cable spool), support the vehicles Kraft Raptor manipulator, monitor cable payout speed and distance and a variable ballast system controlled by the amount of cable deployed. The operational procedure is, launch the vehicle at a BIN platform site with up to 4.5 km of cable on the spool. The vehicle will dive to the BIN, perform the interconnect, and establish a Doppler Velocity Log (DVL) bottom lock and enter coordinates of the location. Using the navigational program ArcNav, the vehicle will proceed along pre-mapped way points. The vehicle will follow the contours 1 to 2 meters off the bottom maintaining visually both the bottom and the cable as it is deployed. The maximum deploy speed will be .5 knot (.9 km) per hour. Deploying approximately 10% more cable length versus distance traveled will avoid tensioning the cable and forming spans. This will be accomplished using a graphic user interface that displays the amount of cable deployed versus the actual distance traveled across the bottom. Pay out speeds will be adjusted manually to match the speed of the vehicle. Upon reaching the BIN, the cable spool will be dropped, as an anchor, holding the excess cable. Using the manipulator, the connector will be removed from a dock within the cable spool body. A 20 meter service loop of cable on the exterior of the cable spool will allow the vehicle to maneuver to the BIN and perform the interconnect. In early July 2006 a successful cable lay of 2,800 meters, between the MOOS mooring and the shelf BIN was performed. In early October the remaining cable lays are scheduled

Automating MBARI's midwater time-series video surveys: The transition from ROV to AUV

MBARI has been conducting remotely operated vehicle (ROV)-based video surveys of the upper 1000 meters of the water column in Monterey Bay, California for over 23 years. These surveys have produced a unique midwater time-series data set that has enabled MBARI scientists to observe changes in mesopelagic animal distribution and community structure in Monterey Bay over that time period. These changes can generally be associated with both short and long term changes in water mass structure, including some now being associated with climate change. This historical data set is becoming even more important as we begin to observe the effects of climate change on community structure and ecology in the midwater environment and try to predict the impact of future change. However, this data set comes at a high cost in ROV and support ship time required to conduct the surveys. In order to sustain these surveys into the future, a more cost effective approach is required. In an effort to reduce cost, improve methodology and develop a system that has the potential to be exported to other institutions, MBARI has developed a high definition video module to be deployed on its Dorado class autonomous underwater vehicle (AUV). This paper explores the challenges of this development, the chosen solutions, and presents early data derived from our initial inter-comparisons of video collected concurrently with MBARIs ROV and midwater imaging AUV.

USE OF AN ELECTRO-OPTICAL-MECHANICAL MOORING CABLE FOR OCEANOGRAPHIC BUOYS: MODELING AND VALIDATION

This paper presents results of numerical modeling of an oceanographic mooring system and makes comparisons to loads measured on a deployed test mooring near Monterey Bay, California. The numerical modeling solves the non-linear equations of motion of the cable in the time-domain. The deployed system is instrumented to monitor environmental loading and the resulting tensions in the mooring cable below the buoy and above the anchor. Comparison of the numerical results to the measured results is useful to refine the accuracy of the model, allowing its use in determining fatigue life of the system and for designing similar systems to be deployed in new locations. This study is part of a project to develop and improve mooring systems for oceanographic use that include an electro-optical-mechanical mooring cable that delivers power and data communication to a network of sea-floor instrumentation. The modeling and test results highlight the engineering challenges associated with designing these systems for long lifetimes.Copyright

Ship to ROV telemetry for Tiburon

A ship to ROV communications system is described that provides an FDDI compatible port for network traffic. Additional traffic including sonar and navigation data is electrically multiplexed with the network data into a hi-directional 250 Mb/second serial bitstream. Six channels of high quality digitized video are also uplinked on a separate 1.25 Gb/second bitstream. Multiplexing permits the system to operate on two optical fibers, allowing efficient cable design.