The Multichannel Acoustic Telemetry System

An acoustic system to measure a descent velocity of a self-contained instrument package is described in this paper. The system is also capable of transmitting two additional time variables. The velocity measurement is based on the Doppler frequency shift of an acoustic signal, while the two other channels use frequency modulated carriers. Errors introduced by heave of a receiving hydrophone is compensated by an integrated signal derived from an accelerometer placed in the hydrophone housing. The results from sea trials are presented and the system performance is evaluated.