An ROV is a Remotely Operated Vehicle that is tethered and under the direct control of a human operator at the surface. An ROV can stop, hover, and bring back an object or water sample to the surface using a manipulator arm or other mechanical device. ROVs range in mass from a few pounds to several tons, with tethers a few 100 meters to full ocean depth in length.
All ROVs possess a video camera or high-frequency imaging sonar to allow the surface operator to drive the vehicle by visual feedback from the image transmitted over the tether. Maneuvering is provided by orthogonal thrusters that allow independent control of vertical and horizontal motion, including rotation around the ROV’s vertical axis. ROVs are usually weighted to almost neutral buoyancy, allowing them to hover. Most ROVs are supplied with power through the tether, although deep-water ROVs may carry battery power on the vehicle instead, and use the tether only for image transmission and other data telemetry.
Almost all ROVs possess a manipulator arm under control of the surface operator that allows for collection of biological or geological specimens. ROVs with sufficient power and size can carry other payloads including Conductivity, Temperature, and Depth (CTD), Acoustic Doppler Current Profilers (ADCPs), sidescan and multibeam sonars, and more specialized payloads like plankton samplers and microelectrodes for porewater studies.
ROVs are most often deployed from a surface ship, and operated a short lateral distance away from the ship. Deep-water deployments may require the surface ship to keep on station using dynamic positioning. Because tether management is a complex task, ROVs are best suited for exploring relatively small (100s of square meters), targeted areas of the seafloor, rather than conducting large-area surveys. Geopositioning of the ROV is provided by acoustic means relative to the surface ship’s position.
ROVs were initially developed by the defense and oil industries. Maturation of the technology coupled with decreases in vehicle cost led to their adoption as a viable research tool by marine scientists.