Office of Marine Programs
University of Rhode Island
Narragansett Bay Campus
Narragansett, RI 02882-1197
Phone: 401-874-6211
Fax: 401-874-6486
Email: OMP@gso.uri.edu
Instrumentation
Over-the-Side Scientific Systems |
| In order to study the vertical and horizontal structure of the ocean, instruments have been developed that are deployed over the side of the ship and send data back to the vessel. When the data has been collected these instruments are recovered from the ocean and brought back onboard where they are maintained and repaired, if necessary. The scientific systems that are routinely deployed from Endeavor are described here. |
| CTD is an abbreviation for “Conductivity-Temperature-Depth”. CTDs are instruments that provide important information to oceanographers about the temperature, salinity and density of seawater. A CTD instrument is lowered through the ocean on a wire and provides data on the vertical structure of the ocean’s temperature, conductivity and pressure. As the package is lowered through the water column data are sent back to the ship where they are viewed by the scientists and recorded on computers. From the pressure data, depths can be calculated. The salinity and density of seawater can be calculated using the conductivity, temperature and pressure data. CTD data can be used to calculate the speed of sound through seawater. Other instruments can be interfaced to a CTD to give information on a variety of biological (chlorophyll biomass), chemical (dissolved oxygen and nutrient concentrations) and physical (light levels) parameters. |
| MOCNESS is an abbreviation for Multiple Opening/Closing Net and Environmental Sampling System. This system allows scientists to sample and study zooplankton and small fish at specific depths in the ocean. Computer commands are transmitted down a cable to the MOCNESS that make nets open and close. Instruments located on the frame of the MOCNESS measure the pressure/depth, salinity, temperature, dissolved oxygen concentration, chlorophyll biomass and particle concentrations. These data are transmitted back up the sea cable to the ship where they are displayed and recorded by computers. With this real-time information, the scientists can choose specific depths in the ocean to sample animals to understand their distribution and abundance in the water column. |
| The Scanfish is a depth-controlled vehicle that moves vertically through the water column as it is towed horizontally behind a ship. The depth of the vehicle is controlled by means of moveable wing flaps. The cable that connects the vehicle to the ship allows power and commands to be sent to the vehicle as it moves through the water and data to be transmitted and displayed on the ship in real-time. The Scanfish is shaped like a wing and carries a payload of scientific instruments, such as a CTD, fluorometers, transmissometers, nutrient and dissolved oxygen sensors, etc., that measure chemical, biological and physical parameters in the ocean. The Scanfish allows the vertical and spatial distribution of properties to be mapped relatively quickly. |
| Onboard the Endeavor, seawater samples are collected with Niskin bottles constructed of PVC that are attached to an aluminum frame called a rosette. Also attached to the rosette is a CTD and other various instruments. Depending on the size of the frame, twelve or twenty-four bottles are used to collect seawater samples. The CTD package has a wire that allows it to be lowered through the water column from the ship with a winch. Once a desired depth to sample the water is reached, the bottles are closed via an electronic signal from the ship. When the package is back on board the ship the scientists can take water samples from the bottles to measure the chemical composition of seawater or to count and identify the plants, bacteria and animals that make up the biological community. Some scientists will incubate the seawater to find out how quickly organisms are growing. |
| XBT is an abbreviation for eXpendable BathyThermograph. The purpose of this instrument is to provide data on the vertical profile of seawater temperature, from the surface ocean to several hundred or thousand meters below the surface, depending on the type of probe used. XBTs are launched from the stern of a ship using either a deck-mounted or hand-held launcher. Once launched, an XBT probe free-falls through the water column with temperature data transmitted back to the ship along a connecting wire. Data are collected until the connecting wire breaks. |
