Inter-seamount acoustic range instrumentation

This Center has set up a unique sonar range between the tops of two seamounts in the Pacific Ocean. The great distance from the end points to shore has precluded the routing of power and control cables to manned stations and has, consequently, given rise to some unusual instrumentation. The transmitting station was pre-programmed on implantment in June 1969 to broadcast a wide variety of frequencies and signal types during a 10-min period every four hours. The 2000-watt peak power demands are satisfied by a nickel-cadmium battery (subjected to 900 psi sea pressure) which, in turn, receives its charge from a 25-watt radioisotope thermoelectric generator. The station "health" is indicated by the battery voltage at the beginning and end of each transmitting period and is conveyed by a 400-nmi telemetry link, nearly half of which is under water. The receiving station employs a specially designed spar buoy whose three taut anchor lines and independently routed hydrophone cables were allowed to free fall to the ocean floor. Data are processed, and stored in this buoy and are telemetered, on command, once each day to shore for further processing.