The autonomous underwater vehicle (AUV) Sentry is following in the wake of its predecessor, ABE, as a fully autonomous underwater vehicle capable of exploring the ocean down to 4,500 meters (14,764 feet) depth. Sentry builds on ABE's success with improved speed, range, and maneuverability. Sentry's hydrodynamic shape also allows faster ascents and descents.
Sentry is an autonomous underwater vehicle (AUV), which means it can operate independently (autonomously) of a human controller. This is especially useful for making long, repetitive or complicated measurements such as mapping large areas of the sea floor. It can be pre-programmed to follow a designated course or carry out a specific task and can also change tasks and directions when it encounters an obstacle or finds something interesting.
Sentry has a streamlined body to reduce drag in the water, help it submerge and surface quickly, and give it stability when maneuvering around obstacles. The vehicle also has four propeller-like thrusters built into its maneuverable foils, or wings, giving Sentry the ability to start, stop, change directions, and ‘fly’ in different ways underwater. It can even hover like an underwater helicopter to do close-up examinations of the seafloor. Sentry is designed to dive as deep as 4,500 meters (3.1 miles) and is powered by more than 1,000 lithium-ion batteries similar to those in laptop computers, which allow it to stay submerged for up to 20 hours.
Sentry carries a superior science sensor suite and enjoys an increased science payload enabling it to be used for both mid-water and near-seabed oceanographic investigations. Sentry produces bathymetric and magnetic maps of the seafloor and is capable of taking digital bottom photographs in a variety of deep-sea terrains such as mid-ocean ridges, deep-sea vents, and cold seeps at ocean margins. Sentry's navigation system uses a doppler velocity log and inertial navigation system, aided by acoustic navigation systems (USBL or LBL). The USBL system also provides acoustic communications, which can be used to obtain the vehicle state and sensor status as well as to retask the vehicle. In addition its standard sensors, Sentry has carried the Nakamura redox potential probe and the Tethys in-situ mass spectrometer.
Like ABE before it, Sentry can be used to locate and quantify hydrothermal fluxes. Sentry is also capable of a much wider range of oceanographic applications due to its superior sensing suite, increased speed and endurance, improved navigation, and acoustic communications. Like ABE, Sentry can be used as a stand alone vehicle or in tandem with Alvin or an ROV to increase the efficiency of deep-submergence investigations.