Acoustic tracking of expendable bathythermographs

Abstract

This paper describes an experiment conducted to determine the feasibility of acoustically monitoring the fall rate of expendable bathythermographs (XBT's). Several XBT casts were monitored using a 20‐kHz narrow beam echo sounder. The XBT's were dropped at approximately 5‐min intervals near the transducer towbody. A magnetostrictive transducer with a conical beam pattern measuring 15° by 25° total beam width was used with a pulse length of 500/μs, an input power of 750 W, and a pulse repetition frequency of 2.08 pulses per s. Receiver output was recorded on analog tape and later digitized at a rate of 5120 samples per s. Results of the experiment prove feasibility of acoustic tracking of XBT's to depths in excess of 200 m. Further studies will be conducted to determine actual fall rates of these devices using acoustic methods. [Work supported by NORDA.]