A prototype for the acoustic triangulation system of the KM3NeT deep sea neutrino telescope

The KM3NeT consortium is designing a research facility with a cubic kilometer-scale neutrino telescope in the Mediterranean Sea. The neutrino telescope will consist of an array of optical modules which detect Cherenkov light from muon tracks. The optical modules are subject to motion in the presence of deep sea currents, and an acoustic triangulation system is needed to determine their positions to provide the required tracking precision and angular resolution for astronomical neutrino source searches. In this paper we will describe one of the solutions proposed for the acoustic system for KM3NeT and the work done in order to develop a prototype. The system consists of an array of affordable transducers that can operate as transceivers in the 20–40 kHz region and withstand the high pressures (up to 500 bar). Versatile associated low-power electronics has been developed, implementing the all-data-to-shore approach. Besides accomplishing the control of signal transmission and reception, it allows for transducer configuration from shore to benefit from varied on-shore signal processing techniques.