Platforms

Platforms are the means by which instruments are delivered to or maintained in the ocean environment they are intended to measure. Platforms take many forms, from highly mobile surface vessels to tethered underwater vehicles to autonomous underwater vehicles to vertical profilers deployed from vessels to fixed bottom-mounted structures and installations. These are only a few of the many ways that instruments can be deployed in the ocean. Some selected important platforms are described here (click on a platform).

Ocean-going research vessels

Coastal research vessels

Fishing vessels

Vertical profilers

Towed vehicles or sleds

Remotely operated vehicles (ROV)

Autonomous underwater vehicles (AUV)

Manned submersibles

Ocean observatories

Coastal ocean observatories

Acknowledgments

Ocean-going research vessels

Figure 1. Photograph of R/V Knorr. Credit: © Woods Hole Oceanographic Institution.
Figure 1. Photograph of R/V Knorr. Credit: © Woods Hole Oceanographic Institution. Enlarge

The traditional platform for research at sea is the research vessel. This may be a vessel built for the purpose or adapted for the same. It may be ocean-going, capable of extended voyages, or suitable only for near-shore work under good conditions. A number of examples are given together with basic specifications.

R/V Knorr (WHOI)

Research Vessel Knorr (Fig. 1) is a U.S. Navy research vessel that is operated for the American ocean research community by the Woods Hole Oceanographic Institution (WHOI). The vessel is part of the University-National Oceanographic Laboratory System UNOLS.

R/V Knorr was built in 1969, delivered to WHOI in 1970, and underwent a major refit in 1991. Its length is 85 m (279 ft), beam 14 m (46 ft), draft 5.8 m (16.5 ft), displacement 2685 long tons (2643 metric tones), range 12,000 nautical miles, cruising speed 12 knots, endurance 60 days. Its complement is 22 crew, 32 scientists, and 2 technicians.

Special capabilities include fully computer-controlled dynamic positioning, station-holding based on an acoustic navigation system or GPS, and an ice-strengthened bow. R/V Knorr has a fully equipped machine shop, five scientific laboratories of total area 331 square meters, two wet laboratories that can be used as hangar or staging area, and two hydraulic cranes, each with lifting capacity of 31,500 kg. Its two hydrographic winches can each carry 10,000 m of 0.322-inch electro-mechanical cable or 9,200 m of ¼-inch wire rope. Its main trawl winch can carry 11,000 m of 0.68-inch armoured cable.


Figure 2. Photograph of R/V Atlantis. Credit: © Woods Hole Oceanographic Institution. Enlarge

R/V Atlantis (WHOI)

Research Vessel Atlantis (Fig. 2) is a U.S. Navy research vessel that is operated for the American ocean research community by the Woods Hole Oceanographic Institution (WHOI). The vessel is part of the University-National Oceanographic Laboratory System UNOLS.

R/V Atlantis was delivered to WHOI in 1997. Its length is 84 m (274 feet), beam 16 m (52.5 feet), draft 5 m (17 feet), and displacement 3454 metric tones (3510 long tons). Its cruising speed is 12 knots, cruising range, 17280 nautical miles, and endurance 60 days. Its complement is 23 officers and crew, 24 scientists, and 13 deep submergence pilots and technicians.

While R/V Atlantis is designed for general-purpose ocean science, it is configured to carry and operate a number of vehicles of the U.S. National Deep Submergence Facility. These include the crewed submersible Alvin, remotely operated vehicle (ROV) Jason, and towed vehicles Argo II and DSL 120.

In support of sampling operations, R/V Atlantis has a computer-controlled dynamic positioning system to maintain station under adverse conditions of sea state and/or wind. For navigation, it has several positioning systems, including a differential Global Positioning System (GPS), Doppler speed log, radars, and fathometer. Communications are effected by single-sideband and VHF radios, INMARSAT, weather facsimile, telex, and e-mail service. Two hydrographic winches are available, each equipped with 10,000-m-long cables. A dual traction/stowage winch system, with 10,000-m-long cables and wire, is also available.

R/V Atlantis has two Navy-owned sister ships: R/V Thomas G. Thompson, which is operated by the University of Washington, and R/V Roger Revelle, which is operated by Scripps Institution of Oceanography, University of California. The NOAA-owned and -operated vessel R/V Ronald H. Brown is nearly identical.


Figure 3. Photograph of R/V Oceanus, shown docked at the Woods Hole Oceanographic Institution. Credit: © Woods Hole Oceanographic Institution. Enlarge

R/V Oceanus (WHOI)

Research Vessel Oceanus (Fig. 3) is a U.S. Navy research vessel that is operated for the American ocean research community by the Woods Hole Oceanographic Institution (WHOI). The vessel is part of the University-National Oceanographic Laboratory Syste UNOLS.

R/V Oceanus was built in 1975, delivered to WHOI the same year, and underwent a major renovation in 1994. Its length is 54 m (177 ft), beam 10 m (33 ft), draft 5.2 m (17.1 ft), displacement 960 long tons (947 metric tones), range 7,000 nautical miles, cruising speed 12 knots, and endurance 30 days. Its complement is 12 crew, 14 scientists, and 1 technician.

The vessel has three scientific laboratories of total area 130 square meters. Its hydraulic crane has a lifting capacity of 18,200 kg. It has a hydraulic A-frame mounted on the stern and a hydraulic boom on the starboard side. It carries an inflatable boat in support of scientific operations. R/V Oceanus has two permanently installed oceanographic winches. One of these can carry 10,000 m of 0.322-inch electro-mechanical cable or 9,200 m of ¼ -inch wire rope. The other can carry 5,000 m of 0.322-inch electro-mechanical cable. A trawl winch can carry 9,200 m of 9/16-inch wire rope, 0.68-inch cable, or 0.68-inch fiber-optic cable.


Figure 4. Photograph of NOAA Ship Albatross IV. Credit: NEFSC Photo Archives. Enlarge

NOAA Ship Albatross IV

Research vessel Albatross IV (Fig. 4) is owned and operated by the National Oceanic and Atmospheric Administration (NOAA). Albatross IV participates regularly in fishery and environmental investigations being conducted by the NOAA National Marine Fisheries Service (NMFS) Northeast Fisheries Science Center in Woods Hole, Massachusetts. It typically works in the Gulf of Maine and Georges Bank and in continental shelf and slope waters from southern New England to Cape Hatteras. It is a major contributor to the periodic groundfish abundance surveys in this region.

R/V Albatross IV was built in 1962, delivered the same year, and commissioned in 1963. Its overall length is 57 m (187 ft), beam 10.1 m (33 ft), draft 4.9 m (16.2 ft), displacement 1,089 tons, gross tonnage 1,115 tons, and net tonnage 413 tons. Its cruising speed is 10 knots, range 3,933 nautical miles, endurance 16 days. Its complement is 20 officers and crew and 14 scientists.

The vessel is configured as a stern trawler. The hull is ice-strengthened. It has five on-board laboratories and a walk-in scientific freezer.


Figure 5. Photograph of NOAA Ship Delaware II. Credit: NEFSC Photo Archives. Enlarge

NOAA Ship Delaware II

Research vessel Delaware II (Fig. 5) is owned and operated by the National Oceanic and Atmospheric Administration (NOAA). It is instrumental in fishery and other biological resource investigations being carried out by the NOAA National Marine Fisheries Service, Northeast Fisheries Science Center in Woods Hole, Massachusetts (NMFS/NEFSC). The Marine Resources Monitoring, Assessment and Prediction Program (MARMAP) surveys, for example, are conducted with R/V Delaware II. It typically works in the Gulf of Maine and Georges Bank and in continental shelf and slope waters from southern New England to Cape Hatteras.

R/V Delaware II was built in 1967, delivered in 1968, and commissioned in 1975. It underwent a “repair to extend its useful life” in 1996. Its overall length is 47.2 m (155 ft), beam 9.1 m (30 ft), draft 5.1 m (16.6 ft), displacement 897 tons, gross tonnage 610 tons, net tonnage 183 tons. Its cruising speed is 10 knots, range 5,318 nautical miles, endurance 24 days. Its complement is 18 officers and crew and 14 scientists.

The vessel is configured as a stern trawler. It has several laboratories and a walk-in scientific freezer

Figure 6. Photograph of Canadian Coast Guard Ship W. E . Ricker. Credit: photo by K. MacGregor -CG979 © Department of Fisheries and Oceans Canada. Enlarge

CCGS W.E. Ricker (DFO Canada)

Canadian Coast Guard Ship (CCGS) W.E. Ricker (Fig 6.) is an ocean-going research vessel, with home port in Nanaimo, British Columbia. It was built in 1978 in Hokkaido, Japan, as a stern trawler for foreign operations. It was converted in 1986 to a Canadian government research vessel.

The vessel length is 58 m, beam 9.5 m, draft 5.2 m, gross tonnage 1104 metric tonnes (mt), net tonnage 416 mt. The cruising speed is 9.5 knots; endurance, 21 days; range, 4800 n.mi. The vessel complement is 7 officers and 13, with 11 spare berths for scientific parties.

The principal duty of CCGS W. E. Ricker is to support science programs and fish research. It is equipped for trawling, gill-netting, longlining, and deploying traps. It can fish to depths of 2300 m.

Coastal Research Vessels


Figure 7. Photograph of CRV Tioga. Credit: © Woods Hole Oceanographic Institution. Enlarge

CRV Tioga (WHOI)

An example of a smaller, coastal research vessel is Coastal Research Vessel Tioga (Fig. 7), owned and operated by the Woods Hole Oceanographic Institution (WHOI). CRV Tioga was delivered to WHOI in 2004. Its length is 18 m (60 ft); beam 5 m (17 ft); draft 1.5 m (5 ft); and displacement, 16.82 metric tonnes (37,000 lbs). Its cruising speed is 20 knots; cruising range, 350 nautical miles; typical endurance, 1 day, occasionally 2-3 days. Its complement is a captain and a mate, one officer, and up to 10 people on day trips.

The vessel is designed for research in the coastal zone and for testing instruments. It provides quick access to local coastal areas, but can work further offshore and closer inshore than is customary for a boat of its size. It also provides a special capability for the Institution’s education program through support of student projects and training.

For the conduct of science, CRV Tioga has a relatively tall and broad A-frame that is mounted on the aft deck, with 4.5-metric-tonne rating. It has two laboratories: a dry/computer laboratory in the pilot house and a wet laboratory below deck. It also has a dive platform and ladder on the transom, large dive locker and shower. Its instrumentation includes an acoustic Doppler current profiler (ADCP), flow-through seawater sampling system, CTD system with conducting wire winch, and meteorological station. Large transducer wells are available for project use, and the transducers can be changed out from inside the boat while in the water. There is also a trawl winch on Tioga. It is capable of heavier lifts than the CTD winch. The winch can be removed to gain work space. The fantail area is 4.5 x 6 m (15 x 20 ft) without the trawl winch.


Figure 8. Photograph of R/V MacGinitie operated by the Seafloor Mapping Laboratory at California State University at Monterey Bay. Credit: CSUMB Seafloor Mapping Laboratory. Enlarge

R/V MacGinitie (CSUMB)

A second example of a small, coastal research vessel is R/V MacGinitie (Fig. 8), which is owned by the California State University at Monterey Bay (CSUMB). It is operated by the Seafloor Mapping Laboratory at CSUMB. This vessel is trailerable, which means that it can be towed on a trailer from port to port, considerably extending its useful range along the west coast of North America.

Fishing vessels

Fishing vessels have a significant history of use in research, being more numerous than dedicated research vessels and often able to respond far more quickly to an urgent need than a major research vessel, whose schedule may be planned years in advance.

In recent years, the Northeast Consortium has fostered collaborative research in the Gulf of Maine with fishers as the principal investigators. This has introduced a number of fishing vessels into research. Engaged vessels have included stern trawlers, purse seiners, and lobster boats.

Vertical Profilers

Many oceanographic measurements are made by means of a wire lowered from vessels at more or less stationary positions. Examples include a conductivity-temperature-depth (CTD) profiler, bottles for collecting water samples at a number of depths, grab for taking samples of the bottom, acoustic transducers or other sonars for making measurements closer to targets of interest, and video camera for inspecting the bottom.

In some cases, the vessel may attempt to maintain a fixed position in geographical coordinates, which is typically done by dynamic positioning. In other cases, the vessel may drift freely, excepting control maneuvers to avoid fouling with the vertical wire.

Lowering a wire with attached sensors, sometimes called a cast, allows a vertical profile to be determined. This is often especially valuable because of the large number of phenomena that vary systematically with depth.

The structure of currents in the water column is an example of a depth-dependent phenomenon. Differences in direction and strength of currents with depth, not to mention the influence of surface currents and wind acting on the deploying vessel, will generally bow the wire, adding a degree of uncertainty to the measurement. This may or may not be important.

Conductivity-temperature-depth (CTD) sensor


Figure 9. Photograph of a CTD rosette with multiple sensors. The CTD is attached to a metal frame, called a rosette or carousel, along with water-sample bottles and other sensors. Credit: NOAA Ocean Explorer. Enlarge

The conductivity-temperature-depth (CTD) sensor or probe, sometimes simply called CTD, is one of the most basic of oceanographic instruments. It allows temperature and salinity to be determined as a function of depth when deployed in a vertical profiling mode. If maintained at a fixed position, it can determine a time series of the same quantities.

In sophisticated CTDs (Fig.9), additional sensors may be attached, for example, to measure pH, dissolved oxygen, fluorescence, and light transmission or optical backscattering, hence turbidity, upwelling radiance, down-welling irradiance and photosynthetically active radiation, among other variables.

Bottles are often attached to larger CTD systems for collecting samples at selected depths. Such Niskin or Niskin-type water bottle samples are typically used for the chemical analysis of nutrients, but also allow some plankton to be sampled for subsequent laboratory analysis, as for determination of species composition and numerical concentration.


Figure 10. Top view of the Moving Vessel Profiler™, with attached Free-Fall Fish body lying on deck. Credit: © Brooke Ocean Technology, Ltd. Enlarge

Figure 11. Illustration of the path of the MVP™ Free Fall Fish body. The numbered events for a typical cast are: Deployment, Free-fall, Maximum depth, and Retrieval. Credit: © Brooke Ocean Technology, Ltd.
Figure 11. Illustration of the path of the MVP™ Free Fall Fish body. The numbered events for a typical cast are: Deployment, Free-fall, Maximum depth, and Retrieval. Credit: © Brooke Ocean Technology, Ltd. Enlarge

Moving Vessel Profiler ™

The Moving Vessel Profiler™ is a commercially available system (Brooke Ocean Technology, Ltd.) for collecting vertical profiles of oceanographic data from a vessel without having to stop or slow down (Fig. 10). The system that makes this possible is a computer-controlled winch that deploys the cable to achieve free-fall conditions, stopping short of the bottom, then returning the instrument package in time for its next deployment (Fig 11).

Some of the instruments that have been carried with this profiler are conductivity-temperature-depth (CTD) sensor, Laser Optical Particle Counter (LOPC), and fluorometer. These have been conformed to or configured on the free-fall body.

Specific systems have been developed for profiling in water depths extending to 30, 100, 200, and 300 m. A fifth system, for profiling to a depth of 800 m at a vessel speed of 12 knots, is planned.

Towed vehicles or sleds

Towed vehicles or sleds are platforms that are controlled by the towing vessel and hydrodynamic forces acting on the vehicle and its tether, and other forces if in contact with the seafloor. Power is typically supplied to instruments on the vehicle by means of the towing cable, which may also serve as the conduit for commands down to the vehicle. Similarly, data are often sent from sensors on the vehicle to the towing vessel.

There is a great variety in towed vehicles. Some carry a single sensor, for example, a sidescan sonar for shallow-water use only. Others carry a large package of instruments for prolonged tows in very deep water.

Figure 12. Photograph of towed vehicle Argo II being launched at sea. Credit: © Woods Hole Oceanographic Institution.
Figure 12. Photograph of towed vehicle Argo II being launched at sea. Credit: © Woods Hole Oceanographic Institution. Enlarge

Argo II (NDSF)

The towed vehicle ARGO II (Fig. 12) is a rather large platform for carrying a variety of sensors to a maximum depth of 6000 m. It is operated by the Woods Hole Oceanographic Institution as part of the National Deep Submergence Facility.

The frame of ARGO II is box-like, with length 4.6 m, height 1.1 m, and width 1.1 m. Its weight in air is 1 metric ton. Its maximum towing speed is 0.5 knot. Because of its typically very deep operation within 3-15 m of the bottom, ARGO II is equipped with compass and gyroscope for heading information, echo sounder for altitude information, strain guage to determine pressure and depth, and acoustic transponder for use with an external system for fine navigation. Two thruster motors are provided fore and aft to control heading.

For imaging applications, ARGO II is equipped with video, still, and electronic cameras, and a variety of lighting, including incandescent lights and strobes. A scanning sonar is mounted for forward imaging or profiling.

Acoustic and video data are transmitted to the towing vessel by means of a fiber-optic cable. A team of five technicians operates the vehicle, monitoring and recording data.

Figure 13. Photograph of towed vehicle DSL 120A. Credit:  © Woods Hole Oceanographic Institution.
Figure 13. Photograph of towed vehicle DSL 120A. Credit: © Woods Hole Oceanographic Institution. Enlarge

DSL 120A (NDSF)

The DSL-120A is a towed vehicle developed by the Woods Hole Oceanographic Institution to carry sidescan sonars to a maximum depth of 6000 m (Fig. 13). It is part of the National Deep Submergence Facility.

The physical dimensions of the vehicle are length 3.3 m, height 1.1 m, width 0.7 m, weight in air 390 kg, and depth capability 6000 m.

In its original configuration, the DSL-120A carried two sidescan sonars, both operating at 120 kHz. Separate pairs of transmitting and receiving arrays were mounted on the two sides of the vehicle for imaging the bottom by backscatter. This is typically done in narrow swaths defined by beams of horizontal beamwidth 1.7 deg that are oriented exactly perpendicular to the vehicle sides. Vertical beamwidths of 50 deg ensure a potentially large lateral coverage. A source level of 218 dB relative to 1 ?Pa at 1 m achieves a range of order 500 m for deployment at about 100 m over the bottom, hence a total swath width of order 1000 m.

At present, the DSL-120A is instrumented with state-of-the-art split-beam sidescan sonars that can both image the bottom by backscatter and measure the depth as determined by relative phases in the split-beam system. The operating frequencies of the sonars are 120 and 200 kHz. The sonars were developed collaboratively by WHOI, the University of Washington Applied Physics Laboratory, and Acoustic Ocean Systems, Inc., in Richland, Washington. The new system can be mounted on other suitably capable towed vehicles.

The vehicle also carries a low-frequency sonar for use in profiling the sub-bottom. The operating frequency of this is 4.5 kHz.

Data from the various sonars are transmitted in digital form up the fiber-optic cable to the towing vessel.

Remotely operated vehicles (ROV)

A remotely operated vehicle, or ROV as it is generally called within the oceanographic community, is an underwater vehicle that is controlled by commands sent over a tether mechanically connected to another platform, e.g., vessel or dock. The vehicle is itself capable of active motion, hence contains the means of propulsion. Typically it also contains a sensing capability for determining attitude and heading, and the means to control these.

The size of ROVs spans an enormous range, from portable, hand-held units to systems weighing several tons. The respective realms of deployment of such ROVs are correspondingly different, from shallow-water to very deep water environments.

 Figure 14. Photograph of ROV Jason II. Credit: © Woods Hole Oceanographic Institution.
Figure 14. Photograph of ROV Jason II. Credit: © Woods Hole Oceanographic Institution. Enlarge

Jason II/Medea (NDSF)

The Jason II/Medea system is a coupled, two-body remotely operated vehicle (ROV), which was developed by the Deep Submergence Laboratory at the Woods Hole Oceanographic Laboratory for real-time optical imaging. The vehicle is part of the National Deep Submergence Facility.

Jason II (Fig. 14) is the vehicle that carries sensors and sampling tools to the site of investigation. Medea serves as a tether-management system to decouple the motion of Jason II from that of the surface vessel. The combined ROV can operate to depths of 6500 m.

The physical dimensions of Jason II are length 3.4 m, height 2.4 m, and width 2.2 m. The weight in air is about 3.3 metric tons. Its transiting speed on the bottom is 0.5 knot. When descending or ascending, the vertical speed is 1 knot, i.e., 0.5 m/s. Propulsion is accomplished by six electric thrusters, each providing 100 N (250 lbs) of thrust.

Jason II is well equipped with cameras. These include three one-chip color cameras for use by the pilot and scientist; three still color cameras to cover the manipulator, basket, and aft region; and one digital still camera. A pencil-beam scanning sonar is also part of the instrumentation complement. A 200-kHz multibeam imaging sonar is available upon request. Various lights are provided for fore and aft illumination.

The vehicle is instrumented with a number of sensors to determine attitude and heading, pressure, and height over bottom. A transponder is used for very-long-baseline navigation.

Two hydraulic manipulators are available, as are a basket and swing arms. The manipulators can lift 70 kg in water. The payload is 130 kg.

Medea controls the movements of Jason II by means of a 35-m-long neutrally buoyant tether. It houses a coiled fiber-optic tether for connection to the support ship. Medea is equipped with a one-chip color camera and silicon-intensified target (SIT) black-and-white camera. These are used for identifying bottom terrain and tracking Jason II when in motion. Medea weighs 360 kg in air.

The combined ROV system can be deployed from a number of vessels. Both it and its control van, which is used by the technical support team during operation of the ROV, can be transported.


Figure 15. Photograph of ROV Triggerfish. Credit: Deep Ocean Engineering, Inc. Enlarge

Triggerfish

Triggerfish, manufactured by Deep Ocean Engineering Inc, is a commercially available, portable ROV capable of working at depths to 150 m (Fig. 15). Its physical dimensions are length 1.1 m, height 0.4 m, and width 0.5 m. Its weight in air is 31 kg. Its thrust in the forward, lateral, and vertical directions is respectively 23, 10.5, and 10.5 kg. Its payload is 6.8 kg, which might include sonars and hydrographic sensors, among other things. An on-board camera, model DOE 18 color zoom camera unit, has a resolution of 470 lines of TV, with viewing angles from 7 to 58 deg. The camera can be tilted over a 180-deg range at the rate of 9 deg/s. Lighting is provided by two 150-W lamps, controlled by an on/off switch.

Navigation is enabled by a fluxgate compass with nominal accuracy ±3 deg. The depth is electronically sensed. An automatic pilot is available for control of heading and depth by operator selection.

Information on the status of the vehicle: heading, depth, count of turns, elapsed time, and water alarm in case of tether leak, is available for display on a video screen.

Autonomous underwater vehicles (AUV)

An autonomous underwater vehicle (AUV) is a vehicle that operates underwater without mechanical connection to the ultimate source of its control. Typically, an AUV is controlled by means of a set of instructions that are held in an on-board computer. However, it may also accept commands or instructions by acoustic or electromagnetic signals.

Power is generally very limited on AUVs, and is needed for propulsion, navigation, and other on-board control systems. Sensors borne by the AUV as payload must consequently operate very efficiently or only occasionally, depending on the duration of a particular mission.

AUVs span the range from quite portable systems, which can literally be hand-carried, to others that weigh tons in air and require sizeable handling and deployment gear. Correspondingly, these vehicles may make limited oceanographic observations on the modest scale of the littoral zone or extensive observations at essentially full-ocean depth. This last term refers typically to 6000 m, for giving access to 99% of the ocean depths.

There is a large and steadily increasing number of AUVs in use. There are a number of very useful links to autonomous underwater vehicles that may be found through a World-Wide Web search.


Figure 16. Photograph of Autonomous Benthic Explorer (ABE) being deployed. Credit: © Woods Hole Oceanographic Institution. Enlarge

ABE Autonomous Benthic Explorer (WHOI)

The Autonomous Benthic Explorer (ABE) was designed and built at the Woods Hole Oceanographic Institution in the mid-1990s (Fig. 16). It is about 3 m in length, weighs 550 kg in air, and has a maximum cruising speed of about 2 knots. It can operate at depths as great as 5000 m. Its dive endurance is typically 16-34 hours.

ABE can carry a variety of sensors and sensor packages. These include conductivity, temperature, and depth recorder; magnetometer for measuring magnetic fields; scanning and multibeam sonar; and video camera. The vehicle is able to perform precision mapping by means of these devices, for example, of fine-scale bathymetry of the Mid-Atlantic Ridge and of thermal mapping in the vicinity of hydrothermal vents.

ABE can also collect physical samples from the bottom when fitted with a wax core sampler. By pressing this onto the substrate, sediment and rocks adhere to the wax and can be brought to the surface.


Figure 17. Photograph of the Autosub under thin ice. Credit: photo by K. Collins © UK Natural Environmental Research Council. Enlarge

Autosub

Autosub (Fig. 17) is a relatively large AUV developed by the Southampton Oceanography Centre at the University of Southampton, UK. Its length is 6.8 m and diameter, 0.9 m. Its cruising speed is about 3.5 knots. At this speed, its endurance is 40 hours, which is limited by propulsion by an battery-powered electric motor. Autosub can work at depths to 1600 m.

In an early, exemplary application, Autosub was able to investigate the possible avoidance effect on Antarctic krill (Euphausia superba) of the passage of a survey vessel, RRS James Clark Ross. In another novel and important application, Autosub succeeded in determining the distribution of krill under the ice of the Weddell Sea.


Figure 18. Photograph of REMUS under deployment from an inflatable boat. Credit: photo by C. Von Alt © Woods Hole Oceanographic Institution. Enlarge

REMUS Remote Environmental Monitoring UnitS (WHOI)

The Remote Environmental Monitoring UnitS (REMUS) is a relatively compact and lightweight AUV, with nominal length 160 cm, diameter 19 cm, and weight in air 37 kg (Fig. 18). Its maximum operating depth is 100 m. The energy content of its lithium-ion batteries is 1 kWh. At a speed of 3 knots (1.5 m/s), REMUS can run for 22 hours; at 5 knots, 8 hours. Recharging the batteries and downloading data takes about 8 hours, which is the turn-around time. REMUS can be programmed to maintain a constant altitude over the bottom, or follow a yo-yo trajectory, among other courses.

A Standard acoustic system on board REMUS is a Marine Sonics Limited sidescan sonar, with identical arrays on port and starboard sides. The operating frequency may be 600 or 900 kHz, allowing backscattering imaging to a range of order 30 m to the side of the vessel, with 256 pixels spanning this lateral distance, hence with near-decimeter resolution. Other acoustic systems are carried for navigation. Optional systems for the scientific payload include the Dual-Frequency Identification Sonar DIDSON, with operating frequencies of 1.1 and 1.8 MHz, but with identical 29-deg field of view; and a high-resolution, low-ambient-light-level video camera, with 53-deg vield of viw and digital output.

Some applications of REMUS have included environmental monitoring, hydrographic surveying, investigation of fishery operations, and scientific sampling and mapping, among other things. Individual swimming fish have been imaged by means of REMUS-mounted DIDSON. Larger aggregations of fish have been detected by the sidescan sonar.

Figure 19. Photograph of SeaBED at the sea surface. It houses electronic and floatation in the upper cylinder and sidescan sonar, lights and other instruments in the lower cylinder. Credit: © Woods Hole Oceanographic Institution.
Figure 19. Photograph of SeaBED at the sea surface. It houses electronic and floatation in the upper cylinder and sidescan sonar, lights and other instruments in the lower cylinder. Credit: © Woods Hole Oceanographic Institution. Enlarge

Figure 20. Schematic diagram of SeaBED showing its principal components. Credit: © Woods Hole Oceanographic Institution.
Figure 20. Schematic diagram of SeaBED showing its principal components. Credit: © Woods Hole Oceanographic Institution. Enlarge

SeaBED (WHOI)

SeaBED is a rather new AUV, which was built with support from the Office of Naval Research and the National Science Foundation. It is owned and operated by the Woods Hole Oceanographic Institution.

A significant design feature of SeaBED is its hovering capability
(Fig. 19). The vehicle is passively stable in both pitch and roll. It is thus easy to control for the purpose of executing systematic surveys. This enables data collected along intersecting or overlapping transects to be expressed in the form of an integrated mosaic. Typical sources of such data are sidescan sonar, multibeam sonar, and video camera, with respective mapping of backscatter, bathymetry, and photographic imagery.

SeaBED is 2 m long, 1.5 m high, and weighs 200 kg in air. It is designed for small-vessel deployment. Its maximum operating depth is 2000 m. Its range of speeds is 0-3 knots. At a speed of 2 knots (1 m/s), it can operate for up to 10 hours, thus covering 36 km in the course of a single mission before the batteries must be recharged.

The vehicle (Fig 20) typically carries an electronic camera with charge-coupled device (CCD), 1280×1054 pixels and 12-bit quantization; strobe at 1-m range from the camera; 300-kHz sidescan sonar, but with maximum operating depth of 300 m; and acoustic Doppler current profiler for navigation.

Figure 21. Photograph of launch and recovery system for HUGIN during deployment. Credit: © Kongsberg Maritime, Inc.
Figure 21. Photograph of launch and recovery system for HUGIN during deployment. Credit: © Kongsberg Maritime, Inc. Enlarge

Figure 22. Illustration of HUGIN indicating various acoustic beams. Credit: © Kongsberg Maritime, Inc.
Figure 22. Illustration of HUGIN indicating various acoustic beams. Credit: © Kongsberg Maritime, Inc. Enlarge

Hugin

HUGIN (Figs. 21, 22) is the name of a large-scale AUV that is commercially available from Kongsberg Maritime, Inc. The HUGIN 1000 model has a maximum operating depth of 1000 m. Its length may vary over the range 4-5 m, depending on the choice or design of the central payload section. Its maximum diameter is 75 cm, and total volume about 1.3 m3. It weight in air is about 650 kg, but it is neutrally buoyant when immersed.

The vehicle can run at speeds from 2 to 5 knots. At 4 knots, it can operate for 24 hours. The energy content of the battery package is 3-15 kWh.

The HUGIN AUV carries a number of navigation sensors, including an inertial measurement unit, Doppler velocity log, pressure sensor, acoustic navigation transponder with upward- and downward-looking transducers. It also carries an independent altitude and forward-looking echo sounder. Its inertial navigation system is aided by a Kalman filter that optimizes data from the various navigation sensors. Navigation can be controlled by the Global Positioning System (GPS) or its differential version, when at the surface. When underwater, navigation can be controlled by acoustic positioning, range and bearing detection from one or multiple transponders, and terrain-following. A synthetic aperture sonar can be employed for micro-navigation.

The payload typically carries a number of sonars, e.g., multibeam sonar, sidescan sonar, synthetic aperture sonar, and/or sub-bottom profiler. It also routinely carries a conductivity-temperature-depth instrument.

HUGIN is typically used for bathymetric mapping and mine reconnaissance, but it has also been equipped with a scientific echo sounder for observation of marine life in the water column. With its navigation capabilities, it can also map benthic animals in their habitat.

The HUGIN 3000 model resembles the HUGIN 1000 model, but with maximum operating depth of 3000 m.

Figure 23. Photograph of the Spray Glider on the fantail of R/V Cape Hatteras. Credit: photo by J. Dunworth-Baker © Woods Hole Oceanographic Institution.
Figure 23. Photograph of the Spray Glider on the fantail of R/V Cape Hatteras. Credit: photo by J. Dunworth-Baker © Woods Hole Oceanographic Institution. Enlarge

Gliders

Gliders are autonomous underwater vehicles whose propulsion is controlled through the buoyancy state of the vehicle. By means of wings, the vertical velocity generated by a displacement change is converted to forward motion. The flight path of a glider is typically oscillatory (Figs. 23, 24).

There are two basic sources of energy that drive gliders. The most widely used source is that of electricity derived from a battery. This is used to inflate a bladder at depth, increasing the vehicle’s displacement volume and generating an upward force. The bladder is deflated at the surface, or at other shallow depth, generating a downward force.

The second source of energy is that of the heat of a thermally stratified ocean. In one glider, a wax melts in the warm surface water, increasing its volume, which is then used to drive a piston to collapse a gas bladder. This decreases the vehicle’s displacement volume, generating a downward force. At depths is much lower, the molten wax solidifies, decreasing its volume and allowing the collapsed bladder to fill anew. The displaced volume thus increases, generating an upward force.

The magnitude of the driving force is determined by the volumetric change in displacement. This is typically 0.5-1% of the total displacement volume. It is a major factor influencing the hydrodynamic design of the vehicle.

Figure 24. Illustration of the path of the Spray Glider. Credit: J. Doucette © Woods Hole Oceanographic Institution.
Figure 24. Illustration of the path of the Spray Glider. Credit: J. Doucette © Woods Hole Oceanographic Institution. Enlarge

Physically, gliders seem to have an optimum shape and size. They are based on long, straight, circular cylinders, with nose cone, stabilizer, and wings. Lengths are typically in the range 150-220 cm, diameter 20-30 cm, wingspan 100-120 cm, mass in air 50 kg, payload 2-5 kg. With these dimensions, the nominal speed is 0.25 m/s.

Depth capabilities, endurance, and range vary considerably with model. Among gliders with electrical power to control the buoyancy state, the Slocum Glider operates at relatively shallow depths not exceeding 200 m for a period of 3-4 months, with range of 2300 km.

The Seaglider can operate to a maximum depth of 1000 m for up to 220 days, with range 4500 km. The Spray Glider can operate at depths to 1500 m for a period up to 330 days, with range 7000 km. The thermally powered Slocum glider is expected to have an endurance and range that are an order of magnitude greater than those of other gliders, with range extending to 30,000 km. Its maximum operating depth is 1200 m.

Some technical issues include glider navigation, control, and communication. This is often done via Global Positioning System and other satellites.

A number of sensors have been carried on gliders. These include CTDs, photosynthetically active radiation sensor, and fluorometer

Manned subersibles

Manned submersibles or underwater vehicles are relatively few in number for carrying a crew, hence requiring a minimum volume that is often relatively large, with the need for life support systems too. Nonetheless, the contributions of manned underwater vehicles to observational science have been and remain of the first rank. In some cases, use of manned vehicles makes possible directed sampling without equal.

DSV Alvin (NDSF)

Figure 25. Underwater view of DSV Alvin. Credit: © Woods Hole Oceanographic Institution.
Figure 25. Underwater view of DSV Alvin. Credit: © Woods Hole Oceanographic Institution. Enlarge

Figure 26. DSV Alvin resting at the surface while divers come aboard. R/V Atlantis awaits nearby. Credit: photo by D. Fornari © Woods Hole Oceanographic Institution.
Figure 26. DSV Alvin resting at the surface while divers come aboard. R/V Atlantis awaits nearby. Credit: photo by D. Fornari © Woods Hole Oceanographic Institution.
Enlarge

Deep Submergence Vehicle (DSV) Alvin (Figs. 25, 26) is operated as a national oceanographic facility by the Woods Hole Oceanographic Institution (WHOI) for the U.S. Navy. The untethered vehicle typically carries one pilot and two scientists to depths as great as 4500 m. Physical dimensions of DSV Alvin are the following: length 7.1 m (23.3 ft), height 3.7 m (12.0 ft), beam 2.6 m (8.5 ft), draft 2.3 m (7.5 ft) when on the surface. Its gross weight is 17 metric tons. Its normal cruise speed is 0.5 knot; cruising range when submerged, 5 km; and nominal endurance, 10 hours. On a typical dive to the maximum operating depth, two hours would be spent descending, four hours working at depth, and two hours for the return ascent.

Observations from DSV Alvin can be made directly through three ports through the pressure hull, each with diameter 12 inches (30 cm). Observations can also be made from three video cameras and two digital still cameras, each externally mounted. A total of 12 lights can be used to illuminate the bottom. Instruments for in-situ measurements for the particular mission can be carried in a basket or sled mounted in front of the vehicle, with maximum load of 450 kg.

DSV Alvin has had a distinguished history of exploration. This has included seafloor spreading at the Mid-Atlantic Ridge, hydrothermal vents, and the discovery of approximately 300 new marine species.

DSV Alvin was delivered to WHOI in 1964. While it has been in continual operation since then, it has also undergone reconstructions and improvements, thus maintaining its state-of-the-art character. Recently, its planned retirement and replacement has been announced.

Ocean observatories

Ocean observatories are physical structures with power and data storage and telemetry systems that serve as platforms for oceanographic data collection over substantial periods of time.

Traditional observatories have been based on surface or subsurface moorings. They have consisted of instrumented cables hanging from a surface float or held vertically by a subsurface float. In some cases, vertical profilers have been attached to moorings. Meteorological data are often collected from such moorings, for example, for archiving and display by the National Data Buoy Center. Data are generally both stored and transmitted to stations ashore by means of satellites or cell phone.

Figure 27. Diagram of a bottom-moored vertical profiler. Credit: J. Doucette © Woods Hole Oceanographic Institution.
Figure 27. Diagram of a bottom-moored vertical profiler. Credit: J. Doucette © Woods Hole Oceanographic Institution. Enlarge

Figure 28. Schematic diagram of a surface drifter. Credit: NOAA Ocean Explorer
Figure 28. Schematic diagram of a surface drifter. Credit: NOAA Ocean Explorer. Enlarge

Figure 29. Locations of GoMOOS moored buoys in the Gulf of Maine. Credit: Gulf of Maine Ocean Observing System (GoMOOS).
Figure 29. Locations of GoMOOS moored buoys in the Gulf of Maine. Credit: Gulf of Maine Ocean Observing System (GoMOOS). Enlarge

Figure 30. CODAR is a land-based high-frequency radar system. Sea surface current is measured at long range, across wide areas, with a single system. Credit: GoMOOS/U. Maine PhOG.
Figure 30. CODAR is a land-based high-frequency radar system. Sea surface current is measured at long range, across wide areas, with a single system. Credit: GoMOOS/U. Maine PhOG. Enlarge

Figure 31. A composite diagram of LEO-15 instrumentation used during a 2000-2001 experiment Credit: © 2002 Rutgers, The State University of New Jersey, Institute of Marine and Coastal Sciences, Coastal Ocean Observatory.
Figure 31. A composite diagram of LEO-15 instrumentation used during a 2000-2001 experiment Credit: © 2002 Rutgers, The State University of New Jersey, Institute of Marine and Coastal Sciences, Coastal Ocean Observatory. Enlarge

Figure 32. Diagram of the Martha's Vineyard Coastal Observatory. Credit: J. Doucette © Woods Hole Oceanographic Institution.
Figure 32. Diagram of the Martha’s Vineyard Coastal Observatory. Credit: J. Doucette © Woods Hole Oceanographic Institution. Enlarge

Buoys

Buoys are popular surface-floating platforms for diverse oceanographic instruments. These are typically moored, or anchored to the seafloor by means of wires, chains, and weights (Fig. 27). The buoy itself typically contains meteorological instruments. It may also contain underwater sensors mounted directly on the buoy or tethered to the buoy. Individual sensors and arrays of sensors may be tethered. In the case of single sensors, the length of the tether is sometimes actively controlled at the buoy, allowing vertical profiling. Data may be stored and/or transmitted by cell phone or satellite.

Drifters

A drifter (Fig. 28) is a platform consisting of at least a surface float that is free to move under the influence of surface or sub-surface forces, including wind and currents. Often a drogue, or device resembling an underwater parachute, is attached to a surface float to enable the drifter to track along a sub-surface current mostly independently of wind and surface wave forces. Drifters may be instrumented with oceanographic sensors. As in the case of buoys, data may be stored and/or transmitted via cell phone or satellite.

Coastal ocean observatories

In addition to traditional observatories, some of which are situated in quite deep water, some rather large coastal observatories are now in operation. Three are described in the following.

Gulf of Maine Ocean Observing System (GoMOOS)

The Gulf of Maine Ocean Observing System (GoMOOS) is an operational oceanographic observatory in the Gulf of Maine (Fig. 29). Through its Internet site, GoMOOS serves data on sea surface temperature, chlorophyll, ocean color, and waves from moored buoy systems, operating Coastal Ocean Dynamics Applications Radar CODAR systems (Fig. 30), and satellite data. It also provides wave and current model forecasts. The buoys individually measure meteorological conditions, sea surface properties, currents, and water properties, with depth and current profiles. Some of the buoys also have bio-optical instruments on board.

Long-term Ecosystem Observatory-15 meters (LEO-15)

The Long-term Ecosystem Observatory-15 meters (LEO-15) is an ocean observatory consisting of a land-based meteorological tower and seafloor nodes in nominal 15-m water depth (Fig. 31). The observatory is located at Rutgers Marine Field Station in Tuckerton, N.J. It is operated by the Rutgers Institute of Marine and Coastal Sciences.

Typical data provided by the seafloor nodes are vertical profiles of temperature and salinity, measurements of dissolved oxygen and chlorophyll concentrations, light transmission and attenuation, and fluorescence, and current profiles, among other variables. Surface waves are measured by means of a bottom-mounted pressure sensor. These observations are known to be effectively limited to waves with periods greater than about 4.5 s; shorter-period waves are observed routinely with surface buoys.

A major goal of LEO-15 is to provide high-quality data for use in ocean forecast models. Many other sensors have been used to supplement those of the observatory itself, including at times AUVs, surface vessels, satellites, and SCUBA divers.

The potential of the observatory for observing marine life such as plankton has been recognized.

Martha’s Vineyard Coastal Observatory (MVCO)

The Martha’s Vineyard Coastal Observatory (MVCO) consists of a shore-based meteorological tower, an offshore tower, and seafloor nodes providing power and data links to the internet (Fig. 32). It is located offshore immediately south of Martha’s Vineyard in Massachusetts. The observatory collects meteorological data at the shore and offshore towers, sea floor temperature, salinity, bottom pressure (to gauge tides), and current profiles with wave-measuring capability. All data are updated every 20 minutes and archived on shore. MVCO is owned and operated by the Woods Hole Oceanographic Institution, and provides guest ports for users to attain their own instrumentation to make additional measurements in the context of the standard observatory observations.

A major goal of the observatory is to collect data necessary to understanding air-sea interactions, especially coupled atmospheric and oceanic boundary layer dynamics at low wind speeds.

The observatory has also been used to determine vertical profiles of plankton composition and concentration with 1-cm resolution. Auxiliary data accompanying these profiles are vertical profiles of temperature, salinity, light transmission, irradiance at five wavelengths, fluorescence, and dissolved oxygen.

Acknowledgments

Many people have contributed materials, principally images, to this section on platforms; we are indeed grateful. In addition to the credits given in the figure captions, we would like to thank J. Irish, A. Morozov, and D. Wegman for their most helpful comments.

Related Links (alphabetical)

ARGO II (NDSF)
http://www.divediscover.whoi.edu/tools/argo.html

AUV ABE (WHOI)
http://oceanexplorer.noaa.gov/technology/subs/abe/abe.html

AUV AUTOSUB (Southampton Oceanography Centre, University of South Hampton, UK)
http://www.soc.soton.ac.uk/aui/

AUV HUGIN (Kongsberg Maritime, Inc.)
http://www.km.kongsberg.com/

AUV REMUS (NDSF)
http://www.whoi.edu/page.do?pid=10079

AUV SeaBED (WHOI)
http://www.whoi.edu/DSL/hanu/seabed/

CCGS W. E. Ricker (Canadian Coast Guard – Pacific Region, DFO Canada)
http://www.pacific.ccg-gcc.gc.ca/fleet-flotte/fleetinfo/wericker_e.htm

CODAR (Coastal Ocean Dynamics Application Radar)
http://gyre.umeoce.maine.edu/gomoos/codar/

CRV Tioga (WHOI)
http://www.whoi.edu/marops/research_vessels/CRV/

CTD (Conductivity, Temperature, Depth sensor)
http://oceanexplorer.noaa.gov/technology/tools/sonde_ctd/sondectd.html

Drifters
http://oceanexplorer.noaa.gov/technology/tools/drifters/drifters.html
http://www.emolt.org/

DSL 120A (NDSF)
http://www.whoi.edu/page.do?pid=15735

DSV Alvin (NDSF)
http://www.whoi.edu/marops/vehicles/alvin/index.html

GoMOOS (Gulf of Maine Ocean Observing System)
http://www.gomoos.org/
http://gyre.umeoce.maine.edu/gomoos/codar/

LEO-15 (Long Term Ecosystem Observatory – 15 meters)
http://marine.rutgers.edu/cool/LEO/LEO15.html

Moored Surface Buoy
http://www.whoi.edu/institutes/occi/currenttopics/ct_oms_outposts.htm
http://www.ndbc.noaa.gov/dart/dart.shtml

MVCO (Martha’s Vineyard Coastal Ocean Observatory)
http://mvcodata.whoi.edu/cgi-bin/mvco/mvco.cgi

MVP™ (Moving Vessel Profiler™, Brooke Ocean Technology, Ltd.)
http://www.brooke-ocean.com/mvp_main.html

NDBC (National Data Buoy Center)
http://www.ndbc.noaa.gov/

NOAA Ocean Explorer
http://www.oceanexplorer.noaa.gov

NOAA Ship Albatross IV (NOAA)
http://www.moc.noaa.gov/al/

NOAA Ship Delaware II (NOAA)
http://www.moc.noaa.gov/de/

NOAA Ship Ronald H. Brown (NOAA)
http://www.moc.noaa.gov/rb/

Northeast Consortium
http://www.northeastconsortium.org/

ROV Jason II/Medea (NDSF)
http://www.whoi.edu/marops/vehicles/jason/index.html

ROV Triggerfish (Deep Ocean Engineering, Inc.)
http://www.deepocean.com/trigger.pdf

R/V Atlantis (WHOI)
http://www.whoi.edu/marops/research_vessels/atlantis/

R/V Knorr (WHOI)
http://www.whoi.edu/marops/research_vessels/knorr/

R/V MacGinitie (CSUMB)
http://seafloor.csumb.edu/capabilities.html
http://seafloor.csumb.edu/MacGinnitespecs.html

R/V Oceanus (WHOI)
http://www.whoi.edu/marops/research_vessels/oceanus/

R/V Roger Revelle (UCSD)
http://shipsked.ucsd.edu/Ships/Roger_Revelle/

R/V Thomas G. Thompson (UW)
http://martech.ocean.washington.edu/

Seaglider (UW)
http://www.apl.washington.edu/projects/seaglider/summary.html

Slocum Glider (Webb Research Corporation)
http://www.webbresearch.com/slocum.htm
http://marine.rutgers.edu/cool/projects/oceanrobots.htm

Spray Glider (Scripps Institution of Oceanography and WHOI)
http://spray.ucsd.edu/
http://www.whoi.edu/instruments/viewInstrument.do?id=1498

UNOLS (University-National Oceanographic Laboratory System, Research Vessels)
http://www.unols.org/info/vessels.htm

WHOI (Woods Hole Oceanographic Institution, Research Vessels)
http://www.whoi.edu/marops/research_vessels/