Reduction to Practice of a Towed Ocean Profiling System

Summary form only given. Various towed devices are utilized in the practice of oceanographic research. The precision of measuring the physical characteristics of the ocean (such as water velocity, temperature, conductivity, etc.) is determined to a great extent by the fixity of the movement in the vertical plane and the velocity of the instrument carrier. During agitation of the ocean surface, the motion of the towing vessel is transmitted (by the tow cable) as a perturbation to the towed unit. This affects the precision of the measure ments and limits the feasibility of their execution. This report describes the design, construction, and field use of a Towed Instrument Platform designed to be towed behind a ship. The unique towing arrangement provides a method for soft coupling the instrument platform to the tow cable and results in significant reduction in platform motion. The Towed Instrument Platform is decoupled from rapid vertical ship motions by a pulley tether attachment above the tow cable depressor. In addition, the unique towing arrangement provides for profiling about the neutral position between the slack tethers. Measurements of platform motion were accomplished using three linear accelerometers, three angular accelerometers, two pendulums and a pressure transducer assembled in a motion monitoring package located in one of the hulls of the catamaran like platform. Actively controlled surfaces on the bow and stern planes connecting the two hulls served to modify the platforms depth and attitude. A pressure transducer in the streamlined depressor served as a reference to compare large-scale motions. A significant reduction in platform motion was demonstrated with certainty.