AVATAR: Second-generation transceiver electronics for ocean acoustic tomography

An Advanced Vertical Array Tomographic Acoustic Receiver (AVATAR) has been designed to replace the receivers, source code generators, and mooring tracking interrogators used in the 1981 Ocean Acoustic Tomography Experiment and the 1983 Reciprocal Transmission Experiment. The system will (i) receive, process, and record data from a small vertical array of hydrophones, (ii) generate the signals to be amplified and transmitted by an acoustic source, (iii) interrogate bottom-mounted acoustic transponders used to track mooring motion, (iv) provide the capability to compare receiver time with shipboard time in situ, and (v) measure pressure and temperature. The system is configured with a powerful central microprocessor (Harris 80C86) controlling a number of single-chip computers (Motorola MC1468705G2) over a lower-speed Interprocessor Bus. In addition to serving as system controller, the 80C86 is used to perform computationally intensive tasks and high-speed tasks, while the single-chip computers perform a variety of simpler functions. The electronics are shock-mounted for protection from source vibration and are designed to fit in a 10-inch I.D. tube. A prototype has been completed. Three units will be fabricated by early 1986 for use in a long-range (1000 km) reciprocal acoustic transmission experiment designed to explore the feasibility of acoustically measuring gyre-scale averages of ocean temperature and velocity. The basic system architecture has been designed with sufficient generality to be useful in many low-power data acquisition or control applications.