ACOUSTIC CORRELATION SONAR FOR VERTICAL PROFILING OF OCEAN CURRENTS TO A RANGE OF 1-KM

Ocean current profilers, based on spatial or temporal correlation anal ysis of sound backscattered from passive targets drifting with the cur rent, have several potential advantages over the more common Doppler p rofilers. Correlation profilers can operate over a longer range with s maller, lighter and cheaper transducers. However, the signal processin g is more complex and computationally intensive, increasing transmissi on intervals and leading to difficulties understanding when and why th e performance is poor. Using data gathered from RRS Discovery in early 1995 the authors describe the performance of a 22kHz acoustic correla tion current profiler and compare its results with a lowered acoustic Doppler profiler. At low ship speeds, the signal to noise ratio was su fficient to allow profiling to 1km depth, with the achievable range re ducing as speed increased. Bias and decorrelation occurred in the uppe r 160m owing to unknown causes and greatly reduced data quality.