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Ocean Gliders: A Technological Revolution for Oceanography

posted Dec 9, 2010, 11:44 PM by Cesar Harada

http://imos.org.au/anfog_instrument.html

Ocean gliders are a new breed of autonomous underwater vehicles (AUV) which harvest their propulsion from the ocean itself. By changing their buoyancy gliders expend very little energy to descend and ascend. A pair of fixed wings, vertical tail fin, rudder and movable internal battery packs steer them during their silent journeys soaring through the oceans.

Being unmanned and fully-submersed, the ocean gliders can work around the clock in all weather conditions continuously sampling the water for temperature, salinity, dissolved oxygen, chlorophyll and turbidity. They fix their positions via the Global Positioning System (GPS) when they surface and communicate with our shore lab via Iridium satellite, relaying collected data and receiving any new commands from the scientists. A typical ocean application would be to monitor boundary currents such as the East Australian, Flinders and the Leeuwin Currents.

ANFOG deploys 2 types of ocean gliders: Slocum gliders and Seagliders. Slocum gliders,  manufactured by Webb Research Corp are optimised for shallow coastal water (< 200m) where high manoeuvrability is needed. Seagliders, built at the University of Washington, are designed to operate most efficiently in the open ocean up to 1000m water depth. Slocum gliders are used in intensive coastal monitoring while the Seagliders are used to gather long-term environmental records.

Inside the Gliders

Inside a Slocum Glider
Inside a Seaglider

Sensors

Currently, our Slocum gliders are instrumented with a Seabird-CTD, WETLabs BBFL2SLO 3 parameter optical sensor (measuring Chlorophyll-a, CDOM & 660nm Backscatter) and an Aanderaa Oxygen optode.

Our Seagliders are equiped with a Seabird-CTD, WETLabs BBFL2VMT 3 parameter optical sensor (measuring Chlorophyll-a, CDOM & 660nm Backscatter) and a Seabird Oxygen sensor.

Links

www.wetlabs.com

www.seabird.com

www.aanderaa.com

 

How it Works

 

Gliders are unmanned vehicles. They are given waypoints to travel to and are monitored by scientists at the shore lab. With the aid of an onboard computer, a glider moves vertically in the ocean by changing its density by inflating/deflating a bladder to adjust its volume to weight ratio. Forward momentum is achieved with a pair of fixed wings and pitching the glider upward or downward by shifting a battery pack aft or fore of the vehicle. Sideways shifts of the battery pack also allow the glider to roll and execute turns.

The glider travels at maximum speeds of 30-40 cm/s (~0.5 knot) moving up and down through the water column in a saw-tooth pattern to a set of targeted waypoints. The glider track can be controlled at any time through commands sent by the scientists via satellite. Temperature, salinity, dissolved oxygen, turbidity, chlorophyll and depth are logged. Additionally, average water velocities can be determined by considering how far the glider has drifted from its expected course. When the glider is at the surface, it fixes its position via GPS and relays the data collected via satellite to a shore station. Depth capabilities of the gliders range from 200 m to 1000 m. The scientific payload of a glider can comprise a range of sensors.

Gliders are a new technology capable of operating over extended regions and time frames including transects of up to a 1000km.

 

Gliders soar in saw-tooth trajectories through the ocean
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