Friday, June 20, 2008

Jason 2: French-US satellite to track sea levels

The French-US satellite Jason 2, slated for pre-dawn lift-off Friday from California, will provide precise monitoring of rising sea levels and currents and track the effects of climate change.

Weather permitting, the high-tech oceanography space lab will be launched aboard a Delta 2 rocket from Vandenberg Air Force Base from 0746 GMT, when a nine-minute window of opportunity for the launch opens.Fifty-five minutes after take-off, it will reach its orbit some 1,335 kilometers (830 miles) above the Earth."We are set to fly," NASA launch manager Omar Baez said on the Spaceflight Now website.

Jason 2 is programmed to maneuver into the same orbit as its predecessor Jason 1, which was launched in 2001, and eventually replace the older craft.Rising sea levels is one of the most serious consequences of global warming, threatening dozens of island nations and massively populated delta regions, especially in Asia and Africa.

Data from previous missions showed that sea levels have risen on average by 0.3 centimeters per year since 1993, or twice as much as they did in the whole of the 20th century, according to marine measurements.But 15 years of data is not enough to draw accurate long-term conclusions, say scientists.

The three-year OSTM (Ocean Surface Topography Mission)/Jason 2 mission will help create the first multi-decade global record of the role of the ocean in climate change, according to scientists at NASA's Jet Propulsion Laboratory in Pasadena, California.It will also provide more accurate forecasts of seasonal weather patterns, and near real-time data on ocean conditions.

"Without this data record, we would have no basis for evaluating change," said the mission's project scientist, Lee-Lueng Fu, in a statement.Fu compared the sea level record begun in 1992 with the continuous measurements of atmospheric carbon dioxide initiated in the 1950s at the Mauna Loa Observatory in Hawaii.

"The Mauna Loa data proved that carbon dioxide levels were indeed rising as had been predicted, and they were the basis for our understanding of the greenhouse effect," Fu said.

"The height of the ocean is another fundamental measurement of our climate. The key is to have rigorous, well-calibrated data collected over a long period of time."Global sea levels are expected to rise in the coming years as the Earth warms, scientists have said.

The oceans act as the planet's thermostat, and absorb more than 80 percent of the heat from global warming, with the rest absorbed by the atmosphere, land and glaciers, NASA scientists have found.Warming water and melting ice are the two main factors contributing to rising sea levels.

The OSTM/Jason 2 mission is a partnership between NASA, the National Oceanic and Atmospheric Administration, the French National Center of Space Studies (CNES) and the European satellite agency EUMETSAT.

Jason 2's most powerful onboard instrument is CNES's Poseidon 3 radar altimeter, which can measure the height of ocean surfaces in relation to Earth's centre with a margin of error of 3.3 centimetres (1.3 inches).



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