Progress Report on the ENDECO Free Fall C.T.D

The vehicle system is designed to meet the World Ocean Circulation Experiment (WOCE) specification and provide a low cost alternative for the oceanographer instead of using ships with hydrographic winches and dedicated C.T.D. systems. The vehicle is tracked using a pressure coded acoustic pinger synchronized to an IBM compatible computer aboard the deployment vessel. With horizontal range derived from these measurements, the vessel can manoeuvre to the pick up site. A new temperature and conductivity sensor developed under a Department of Energy SBIR grant is designed to allow at-sea calibrations in the Triple Point of Water and Gallium standard temperature cells. Water samples are obtained using 12 evacuated pyrex glass 250 ml sample bottles with special break-off fill caps. The round-trip travel time for the Free Fall C.T.D. is approximately 1 hour to 6500 m compared to 4 hours using conventional techniques.