How ABE Works

ABE operates autonomously from the support research vessel. It has no tether, and is controlled in real-time by onboard computers using its own rechargeable batteries for all power. Upon launch, ABE descends to the seafloor with the help of a descent weight that is released after safe arrival at depth. On most dives ABE uses acoustic long-baseline transponder navigation with (when close enough to the seafloor) bottom-lock acoustic Doppler measurements to determine its position and velocity over the seabed. ABE descends at 15-20 m/minute following a controlled spiral trajectory to ensure that it reaches the desired starting point while consuming minimal energy.

After reaching the seafloor and performing a series of checks, ABE releases its descent weight to become neutrally buoyant and begins its pre-programmed survey. A dive can consist of any mix of water column investigations (e.g. hydrothermal plume surveys) at constant water depths, seafloor geophysical investigations at fixed heights above the seafloor (anywhere from 50-200 m off depending on the application: e.g. magnetics, high-resolution bathymetric mapping) and digital photography at a height of just 5 meters above the seafloor. ABE usually surveys until either it reaches the end of its program or its batteries are depleted (typically between 20-30 km along track and 15-30 hours of survey time, depending on sensor payload, survey type, and terrain). At the end of its dive, ABE releases two ascent weights to become positively buoyant and return to the surface at 15-20 m/minute.