Free Fall, Wire Guided Rosette Water Sampling System

Features:

• Decouples instruments from ship heave
• Improved CTD data quality
• Eliminates the need for motion compensated winch systems
• Ability to work in more severe sea states
• Reduced chance of cable damage
• Improved lowering speed
• Multiple sensor suite capability
• Proven General Oceanics CTD and Rosette Technology
• Simple wire rope operation
• Accepts standard bottles sizes
• CTD and Rosette easily separated for individual use
• Optional Datasonics acoustic modem connection for real time "snapshot" data collection
• Internal CTD data logging and automatic Rosette control when MERMAID is installed
• Optional LADCP mounting and data integration

The General Oceanics Wire Guided Free Fall Profiler, developed and licensed under agreement from Quissett Development Corporation a subsidary of Woods Hole Oceanographic Institution, Woods Hole MA. 02543, is the next generation system for oceanographic sampling.

Unlike a conventional frame that is fixed to the end of an electromechanical cable, this new frame is free to slide vertically along it's tether. Allowing the frame to move relative to the sea cable decouples the underwater instrumentation from ship roll on down-cast. Improved data quality from CTD instrumentation and the ability to work in more severe sea states is the result. The chance of cable damage that occurs when wire speed exceeds the terminal velocity of conventional underwater packages is greatly reduced.

The standard frame is equipped with the General Oceanics' MERMAID, an intelligent data logger and Rosette controller. The MERMAID system provides CTD data logging, Rosette control and communication with the ship when either a Datasonics acoustic modem or inductive data coupling is used. Low speed, subsampled data telemetered to the surface provides the operator with a real time plot of downcast data. With this information, the operator may determine at which depths bottles should be taken during the upcast. The operator may then either program the MERMAID to close bottles automatically or may manually command the MERMAID to close bottles through the modem telemetry.

The minimum MERMAID configuration consists of a 386 CPU, RAM memory, 500 Mbyte Hard Disk Drive and 3 serial ports. The MERMAID, which runs OCEANSOFT I CTD data acquisition software, performs all of the functions in a self-contained package in the same manner as if data was collected real time on board the research vessel. CTD data is stored in the same format and ready to download for post-processing once the system is retrieved.

This system may be configured to accept standard Niskin or GO-FLO sampling bottles, a MK3C/WOCE CTD, and other sensors such as a fluorometer, transmissometer, PAR light sensor, altimeter and LADCP.

The schematic below illustrates a 36 position, 10 liter bottle, wire guided, free-fall frame at close approach to the wire stop. The overall height of this system is 2.235 m., diameter across the sample bottle ring is 1.4 m. The mass of the frame and complement of bottles is 375 kg. Typical instrumentation increases this to around 525 kg.

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