koldunovn
6th January 2006, 10:56 PM
JOHN ANTCZAK (Associated Press)
LOS ANGELES - Topex-Poseidon, the durable U.S.-French spacecraft that made El Nino a household term as it revolutionized understanding of the role of ocean temperature on climate, has been decommissioned after circling the globe 62,000 times over 13 years.
Topex data converted to colorful graphics made the public see the oceans as splotches of temperature-indicating green, blue, purple, orange and white that sometimes signified the onset of the climate-altering Pacific warming phenomenon called El Nino or its opposite, the cool, dry La Nina.
A device called a pitch reaction wheel that helped keep the satellite oriented stalled on Oct. 9 and after several months of attempts at a fix, NASA's Jet Propulsion Laboratory on Thursday announced that the mission was over.
Launched Aug. 10, 1992, the spacecraft was only expected to last three to five years but funding continued as it kept operating. The total mission cost was approximately $600 million, divided between NASA and France's Centre National d'Etudes Spatiales, JPL spokesman Alan Buis said.
The main instrument on Topex - short for ocean surface topography experiment - was a NASA radar altimeter that bounced radio pulses off the Earth, enabling sea surface height to be determined to within a few centimeters. Sea surface height changes with temperature so altimeter measurements are means to determine how much heat is stored in any given area of the ocean and how that changes.
Topex also carried a French altimeter which at the time was experimental and is now a proven technology.
"Before the launch of the mission ... we did not have a global ocean observing system equivalent to the weather network," Topex-Poseidon project scientist Lee-Lueng Fu said in an interview.
Topex covered 95 percent of ice-free oceans every 10 days.
"Essentially what happened was that quantitatively we had our fingers on the pulse of the global oceans for the first time in history," said Bill Patzert, a JPL research oceanographer. "We collected more data in the first year than they had in the previous century of data."
El Nino, Spanish for "little boy," was the term South American fisherman used to describe changes in the sea and fishery, usually around Christmas times, during periodic warming of the tropical Pacific Ocean.
El Nino was well-known in the scientific community but before Topex it was thought to be restricted to a narrow band around the equatorial Pacific because of a lack of observations, Fu said.
"Then we captured this global view of how an El Nino developed and how it was affected by larger-scale circulation of the ocean," he said. "And also through the dramatic imagery we produced ... the public became aware of this devastating climate event."
El Ninos are linked to unusually heavy rain in the central and eastern Pacific and drought in the western Pacific. For example, the U.S. West Coast can be unusually stormy while northern Australia becomes unusually dry.
Topex launched just in time for a mild El Nino in 1993, followed by another mild one in 1995, said Fu, noting that there is controversy in declaring an El Nino because of changing definitions. Then, in 1997, Topex detected what Fu called "the biggest El Nino of the century."
The 1997-98 El Nino caused an estimated $20 billion in damage worldwide.
Before it was done, Topex detected a fourth El Nino in 2002, Fu said.
As Topex's data record grew longer, scientists were able to see long-term processes in the oceans including what is called the Pacific Decadal Oscillation, a massive oceanwide shift of heat content.
Topex's uniform global measurements, in place of sparsely located tide gauges around the world, established that there was a trend of sea level rise, Fu said.
The craft's Global Positioning System receiver, which was experimental at the start of the mission, has become standard technology for precision determination of orbit, he said.
A successor spacecraft, Jason 1, has flown in tandem with Topex since its Dec. 7, 2001, launch and another craft called the Ocean Surface Topography Mission is scheduled for launch in 2008.
Topex was left to keep circling the Earth in its 830-mile-high orbit. Patzert noted that aside from its failed balance wheel, Topex still has fuel and most of its instruments still work.
"This is not a wake: This is a celebration of a remarkable mission," he said.
credits to: http://www.mercurynews.com/mld/mercurynews/news/breaking_news/13560536.htm
ON THE NET
JPL: http://www.jpl.nasa.gov (http://www.jpl.nasa.gov/)
LOS ANGELES - Topex-Poseidon, the durable U.S.-French spacecraft that made El Nino a household term as it revolutionized understanding of the role of ocean temperature on climate, has been decommissioned after circling the globe 62,000 times over 13 years.
Topex data converted to colorful graphics made the public see the oceans as splotches of temperature-indicating green, blue, purple, orange and white that sometimes signified the onset of the climate-altering Pacific warming phenomenon called El Nino or its opposite, the cool, dry La Nina.
A device called a pitch reaction wheel that helped keep the satellite oriented stalled on Oct. 9 and after several months of attempts at a fix, NASA's Jet Propulsion Laboratory on Thursday announced that the mission was over.
Launched Aug. 10, 1992, the spacecraft was only expected to last three to five years but funding continued as it kept operating. The total mission cost was approximately $600 million, divided between NASA and France's Centre National d'Etudes Spatiales, JPL spokesman Alan Buis said.
The main instrument on Topex - short for ocean surface topography experiment - was a NASA radar altimeter that bounced radio pulses off the Earth, enabling sea surface height to be determined to within a few centimeters. Sea surface height changes with temperature so altimeter measurements are means to determine how much heat is stored in any given area of the ocean and how that changes.
Topex also carried a French altimeter which at the time was experimental and is now a proven technology.
"Before the launch of the mission ... we did not have a global ocean observing system equivalent to the weather network," Topex-Poseidon project scientist Lee-Lueng Fu said in an interview.
Topex covered 95 percent of ice-free oceans every 10 days.
"Essentially what happened was that quantitatively we had our fingers on the pulse of the global oceans for the first time in history," said Bill Patzert, a JPL research oceanographer. "We collected more data in the first year than they had in the previous century of data."
El Nino, Spanish for "little boy," was the term South American fisherman used to describe changes in the sea and fishery, usually around Christmas times, during periodic warming of the tropical Pacific Ocean.
El Nino was well-known in the scientific community but before Topex it was thought to be restricted to a narrow band around the equatorial Pacific because of a lack of observations, Fu said.
"Then we captured this global view of how an El Nino developed and how it was affected by larger-scale circulation of the ocean," he said. "And also through the dramatic imagery we produced ... the public became aware of this devastating climate event."
El Ninos are linked to unusually heavy rain in the central and eastern Pacific and drought in the western Pacific. For example, the U.S. West Coast can be unusually stormy while northern Australia becomes unusually dry.
Topex launched just in time for a mild El Nino in 1993, followed by another mild one in 1995, said Fu, noting that there is controversy in declaring an El Nino because of changing definitions. Then, in 1997, Topex detected what Fu called "the biggest El Nino of the century."
The 1997-98 El Nino caused an estimated $20 billion in damage worldwide.
Before it was done, Topex detected a fourth El Nino in 2002, Fu said.
As Topex's data record grew longer, scientists were able to see long-term processes in the oceans including what is called the Pacific Decadal Oscillation, a massive oceanwide shift of heat content.
Topex's uniform global measurements, in place of sparsely located tide gauges around the world, established that there was a trend of sea level rise, Fu said.
The craft's Global Positioning System receiver, which was experimental at the start of the mission, has become standard technology for precision determination of orbit, he said.
A successor spacecraft, Jason 1, has flown in tandem with Topex since its Dec. 7, 2001, launch and another craft called the Ocean Surface Topography Mission is scheduled for launch in 2008.
Topex was left to keep circling the Earth in its 830-mile-high orbit. Patzert noted that aside from its failed balance wheel, Topex still has fuel and most of its instruments still work.
"This is not a wake: This is a celebration of a remarkable mission," he said.
credits to: http://www.mercurynews.com/mld/mercurynews/news/breaking_news/13560536.htm
ON THE NET
JPL: http://www.jpl.nasa.gov (http://www.jpl.nasa.gov/)