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TOPEX/Poseidon, the U.S./French ocean-observing satellite, successfully completed its three-year prime mission to help scientists understand how the Earth's oceans affect our climate.

Having passed the third anniversary of its launch on Aug. 10, 1992, TOPEX/Poseidon has begun its extended mission. Given the health of the satellite, the project management team believes TOPEX/Poseidon will continue to operate at least four more years.

TOPEX/Poseidon's primary science goal is to improve understanding of how oceans circulate. The satellite information is enabling oceanographers to study the way the oceans transport heat and nutrients and how the oceans interact with weather patterns.

"The extended mission will help us further achieve TOPEX/Poseidon's primary science goal which is to improve our knowledge of how the oceans circulate," according to Dr. Lee-Lueng Fu, the TOPEX/Poseidon project scientist at JPL. "We are interested in answering questions about long-term variations in the ocean and understanding what role the ocean plays in long-term global change."

The satellite was launched from the Arianespace Guiana Space Center in Kourou, French Guiana by an Ariane 42P booster rocket. It was the first NASA satellite launched by Arianespace from European Space Agency's Guiana Space Center.

The satellite, a joint program of NASA and the Centre Nationale d'Etudes Spatiales, the French space agency, uses a radar altimeter to precisely measure sea-surface height. Scientists are using the TOPEX/Poseidon data to produce global maps of ocean circulation. The satellite has provided oceanographers with unprecedented global sea level measurements that are accurate to less than 5 centimeters (2 inches).

In its more than 14,000 orbits of Earth since launch, the satellite has obtained the following scientific results: In early 1995, oceanographers confirmed that TOPEX/Poseidon had detected a new El Nio condition in the equatorial Pacific Ocean. This condition has been linked to the unusually rainy weather in California and the unseasonably warm winter in the Northeast United States. Preliminary results using data acquired from December 1992 to September 1994, indicate a global rise in sea level of 3 millimeters (0.12 inches) per year. By tracking sea level over the extended mission, TOPEX/Poseidon will help scientists understand whether this rise is a short-term variation or part of a long-term trend. In late 1994, TOPEX/Poseidon helped scientists understand that the climatic effects caused by the El Nio phenomenon are much longer lived than previously thought. TOPEX/Poseidon tracked the residual effect from the El Nios of 1982-83, 1986-87 and 199193. In the Gulf of Mexico, data are helping scientists and a U.S. oil company study potentially dangerous ocean phenomena, called eddies, that can disrupt off-shore oil drilling. In another application, the precision of the satellite's ocean measurements has enabled scientists to calculate global tides across all the open oceans, an important step toward monitoring global ocean circulation from space and understanding the complexities of global climate change.

"The data set from this prime mission significantly exceeds all pre-launch expectations and has provided oceanographers with their first global ocean data set on the Earth's oceans," said Charles Yamarone, the JPL TOPEX/Poseidon project manager. "The satellite is healthy and its critical components are performing at or above expectations which would allow for more than a total of seven years of flight operations," according to Yamarone.

More than 1,400 data images are available through JPL's public access computer site via by anonymous file transfer protocol (ftp) at the address TOPEX/Poseidon data are also available via Internet by World Wide Web at the address, or by dial-up modem to the telephone number +1 (818) 354-1333.

TOPEX/Poseidon is part of NASA's Mission to Planet Earth, a coordinated, long-term research program to study the Earth as a single global environment. JPL manages the U.S. portion of the mission for NASA's Office of Mission to Planet Earth.

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