Images(2)

Expendable Bathythermograph (XBT)

Date2011

Object number00055781

NameBathythermograph

Mediumplastic, metal

DimensionsOverall: 238 × 480 × 105 mm, 2069 g

ClassificationsTools and equipment

Credit LineAustralian National Maritime Museum Collection Gift of CSIRO

Terms

DescriptionAn Expendable Bathythermograph (XBT). An XBT is a hand-held device that launches a single-use probe to record temperature data versus depth in the ocean. It can be deployed onboard any type of research vessel, such as RV Investigator, while the ship is underway.HistoryThe Expendable Bathythermograph (XBT) system was first deployed in the North Atlantic Ocean in 1966 and has been reliably used for over 30 years. It replaced the mechanical bathythermograph (MBT) by using a thermistor and electronic data acquisition system that can record deeper profiles. In 1967 XBT's became operational as part of the Global XBT Network that has been collecting ongoing temperature profile data of repeated transects. An XBT is made up of a launcher and expendable probe with a data processing and recording system that records a temperature profile as the probe descends the water column. There is a copper wire that connects the probe to the launcher as it enters the water at a known rate. It begins to transmit data back onboard the ship once the electrode in the probe touches the water. When the length of the wire has unravelled, the XBT is released and makes it way to the seafloor. Using an XBT is an economical way of recording water temperature to accuracies of +/-0.1°C as a function of depth and can be used in conjunction with other recording equipment to create water column profiles. One of the key reasons for XBT’s uses, is that even when launched from a vessel continuing at full speed, it can still record substantial depths. SignificanceThe XBT is used to collect data for oceanographic and climate studies whilst helping mapping operations. When used on ships that follow repeated routes or along fixed transects, XBT’s are able to help create high-density transect information. One of the key reasons for XBT’s uses, is that even when launched from a vessel continuing at full speed, it can still record substantial depths.