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14.03.2011 23:40 Age: 7 yrs
Category: SRS

Satellite calibration and validation moorings featured on the ABC

The ABC reporter Selina Bryan interviewed Dr Christopher Watson and IMOS Director Tim Moltmann recently.

Tasmanian scientists have developed GPS buoys to check
the accuracy of satellite sea level measurements. (ABC TV)

Tasmanian scientists are using state-of-the-art GPS buoys to measure sea level rise.

The buoys were deployed for the first time earlier this month about 30 kilometres off Bruny Island in Tasmania's south-east.

Christopher Watson from the University of Tasmania said the data collected would be critically important to understanding how oceans are responding to global warming.

"We're the only calibration site in the Southern Hemisphere," he said.

"The technique we use is to deploy a series of oceanographic moorings, as well as these GPS buoys on the ocean surface."

The buoys stay out for two days and take precise measurements twice every second.

Those measurements are then compared to ones taken by satellites.

"That's a basically fundamental system for us to be able to derive sea level using a different technique to the satellites so that we can compare one to the other and make that assessment of their accuracy," Dr Watson said.



Every ten days or so the satellite flies over Bass Strait and Tasmania, crossing Bruny Island.

The crossing only lasts a second, but that is all the time it takes to measure the height of the sea surface.

"The satellite altimeters we are working with here are the tool of choice for measuring sea level rise and that sea level rise globally is a little over three millimetres per year," Dr Watson said.

The scientist said precise measurements push the satellite systems to their limit, so checking their accuracy is vital.

"We're basically calibrating and validating these satellites to achieve that accuracy," he said.

The data taken from the buoys contributes to work by international teams from the US and French space missions.

Tim Moltmann is the director of the Integrated Marine Observing System, which funded the work.

"This work is particularly important because Australia doesn't fly its own satellites, but we benefit hugely from the information we get from satellites," he said.

"The important role we can play is to put instruments in our region like the ones we're talking about here and provide the measurements that enable those satellites to give us much more accurate, better information about what's happening in the Australian region."

Mr Moltmann says it is important to continue collecting the information for long-term monitoring of sea levels.

"This gives us a seat at the international table so as new missions are flown [and] we're seen to be a partner in those processes and we're involved," he said.

"If we're not involved we won't benefit from the information, so it's very important in the long-term."

News story from the ABC website. To watch a video please visit the ABC news site below: