3D acoustic imaging applied to the Baikal Neutrino Telescope

TL;DR

This paper demonstrates a novel 3D acoustic imaging method for localizing underwater neutrino telescope components using passive signals, achieving high accuracy without active acoustic elements, suitable for large-scale neutrino observatories.

Contribution

The study introduces a passive 3D acoustic imaging system for underwater neutrino telescopes, avoiding active elements and providing precise localization of telescope components.

Findings

Localized objects with ~0.2 m accuracy along the beam

Achieved ~1.0 m accuracy transversely

Proposed a layout for stationary 3D imaging setup

Abstract

A hydro-acoustic imaging system was tested in a pilot study on distant localization of elements of the Baikal underwater neutrino telescope. For this innovative approach, based on broad band acoustic echo signals and strictly avoiding any active acoustic elements on the telescope, the imaging system was temporarily installed just below the ice surface, while the telescope stayed in its standard position at 1100 m depth. The system comprised an antenna with four acoustic projectors positioned at the corners of a 50 meter square; acoustic pulses were "linear sweep-spread signals" - multiple-modulated wide-band signals (10-22 kHz) of 51.2 s duration. Three large objects (two string buoys and the central electronics module) were localized by the 3D acoustic imaging, with a accuracy of ~0.2 m (along the beam) and ~1.0 m (transverse). We discuss signal forms and parameters necessary for improved 3D acoustic imaging of the telescope, and suggest a layout of a possible stationary bottom based 3D imaging setup. The presented technique may be of interest for neutrino telescopes of km3-scale and beyond, as a flexible temporary or as a stationary tool to localize basic telescope elements, while these are completely passive.