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Porpoise-like sub swims with the current
Thursday, 16 April 2009 Darren Osborne
The researchers believe the submarine will provide a new perspective on the oceans surrounding Australia (Source: CSIRO)
A remote-controlled submarine built to monitor ocean conditions and move through the water like a porpoise has just completed a successful trial off the coast of Tasmania.
Known as SG-154, the hot-pink submarine measured variables such as temperature, salinity, oxygen and turbidity during its two-month, 1500 kilometre sojourn in the Tasman Ocean.
The submarine, which is a joint project between the CSIRO and the Integrated Marine Observation System, will become part of the ever-growing network of ocean sensors.
CSIRO researcher Ken Ridgway says a fleet of eight remote-controlled submarines will soon be gathering near-real time data about ocean conditions around Australia.
"We have one being put out next week and another being launched from South Australia about the same time," he says. "Eventually we'll have three coastal gliders … and five deep-sea gliders operating."
According to Ridgway, the fleet will primarily be used to record ocean conditions in the East Australian and Leeuwin currents.
"Ocean currents around Australia are critical to so many aspects of nature and human activity," he says. "With the East Australian and Leeuwin currents, we need to understand how they change from season to season and year to year, and the extent of their influence on local coastal conditions, as this affects climate, weather, fisheries, shipping and more.
Ridgway says remote submarines are already being used by marine research groups in the northern hemisphere, but this is the first time one has been developed to measure conditions in the deep ocean.
He says because the submarines are steerable, they can collect data about ocean currents that isn't possible using moored or drifting instruments, and at a fraction of the cost of research vessels and satellites.
To steer its course the submarine uses a porpoising motion, which gives it the ability to descend to a depth of nearly 1000 metres. An inflated oil-filled chamber helps regulate depth changes, while a set of winged gliders help stir the submarine.
Commands are sent to the submarine via the Iridium satellite phone network, and an onboard global positioning system helps it record its position.
"The submarine sends information every time it comes to the surface, about every six hours, and it sends the data via satellite," says Ridgway. "We receive that and then send it the location we want it to head for. It came be programmed with several of these ahead of time."
Ridgway admits the submarine test was as much about learning how to pilot the glider as it was about collecting data.
"It doesn't have any propulsion to help it move forward or backwards - it just glides. So if the currents are too strong it can be a real problem," he says. "We really had to work within what we could do."