Toward an Autonomous Communications Relay for Deep-Water Scientific AUV Operations

We are developing an over-the horizon deep-water autonomous underwater vehicle (AUV) supervision capability by introducing a second autonomous vehicle, an autonomous surface vessel (ASV) with continuous access to Iridium satellite communications, that acts as a communications gateway between operators on the ship or on shore and the AUV. This enables operators to monitor dive progress remotely, including uplinking science data and optionally modifying the AUV's mission in response, frees the ship to conduct other operations remote from the AUV, and enables new operations paradigms. An important question is whether these benefits outweigh the costs associated with managing another vehicle and the degradation in navigation and map quality that results from operating outside the range of the ship's Ultra-Short BaseLine (USBL) positioning system. We undertook trials in 2018 with the Sentry AUV and an LRI Wave Glider ASV, operating the system for a total of 15 Sentry dives. The Wave Glider was recovered once for a planned 24 hr hardware upgrade but otherwise remained deployed for nearly all of our time on station. We report the coordination algorithm employed, along with assessments of system performance in terms of acoustic link reliability, the impact on post-processed AUV navigation from the absence of the ship, and logistical footprint-the impact of the system on the Sentry operations team and other ship operations.