Performance of a Low-Power One-Way Travel-Time Inverted Ultra-Short Baseline Navigation System

We report the performance of a low-power one-way travel-time inverted ultra-short baseline (OWTTIUSBL) system designed specifically for use on long endurance autonomous underwater vehicles (AUVs), as deployed during trials in late 2020. The system consists of a WHOI Micromodem-2 as the acoustic processing core coupled with a MEMS attitude and heading reference system (AHRS) and bespoke four-channel array. At low tilts our system provides standalone position fixes to better than ±5° azimuth at slant ranges in excess of 1500 m. The system consumes 1.1 W when active and is capable of entering a low-power 10 mW sleep mode sufficient to maintain its time base. These specifications are based on data collected with the device lowered from a vessel and excited by a mobile source on the vessel’s small boat. We further present preliminary results from the device as installed on a Seaglider that show the potential for improved low-power navigation insensitive to temporal or depth-dependent variations in current profile.