It’s been sailing the blackness of space now for a decade: a silent
sentinel, watching over the world’s oceans, looking for signs of the
mysterious El Nino and La Nina phenomena whose cantankerous
dispositions wreak havoc on our weather.

TOPEX/Poseidon, a joint NASA-French Space Agency mission to study ocean
circulation and its effect on climate, turned 10 on Saturday. Some
46,763 orbits after launch on an Ariane 42P rocket from the Guiana
Space Center in Kourou, French Guiana, this spacecraft, designed to fly
three to five years, continues to precisely map the surface height of
95 percent of Earth’s ice-free oceans every 10 days. In doing so, it
has revolutionized the study of Earth’s oceans.

Best known for its ability to monitor the progress of large-scale ocean
phenomena like El Nino, La Nina and a long-term ocean feature called
the Pacific Decadal Oscillation that waxes and wanes every 20 to 30
years, this longest-running Earth-orbiting radar mission has amassed
some impressive achievements.

Its continuous data on sea surface height, wind speed and wave height
have given us a new understanding of how ocean circulation affects
climate. The satellite provides input for long-term climate forecasting
and prediction models. TOPEX/Poseidon produced the first global views
of seasonal current changes. It maps year-to-year changes in upper-
ocean heat storage. The satellite has improved our understanding of
tides, producing the world’s most precise global tidal maps and
demystifying deep-ocean tides and their effect on ocean circulation. It
monitors global mean sea-level changes, an effective indicator of the
consequence of global temperature change. Its data are input into
atmospheric models for forecasting hurricane seasons and individual
storm severity. And the satellite has improved our knowledge of Earth’s
gravity field.

“TOPEX/Poseidon has revolutionized the ocean sciences,” said Dr. Lee-
Lueng Fu, TOPEX/ Poseidon project scientist at NASA’s Jet Propulsion
Laboratory (JPL), Pasadena, Calif. “For the first time, the great pulse
of the oceans — ocean eddies, seasonal cycles and year-to-year climate
signals — has been mapped with unprecedented accuracy, yielding
fundamentally important information for testing ocean circulation

“TOPEX/Poseidon data help forecast short-term changes in weather and
longer-term climate patterns,” said JPL oceanographer Dr. William
Patzert. “Ocean currents flow around highs and lows of oceanic
pressure, distributing the Sun’s heat across the globe and releasing It
back into the atmosphere as water vapor, which is returned to the
oceans and land as rain or snow. Understanding the oceans’ behavior is
the key to forecasting climate change.”

Nearly 400 science users worldwide apply TOPEX/Poseidon’s data in a
variety of ways. Fishermen use the data, along with sea-surface
temperature imagery, to locate fish. Satellite altimetry is used to
identify key habitats for other marine animals, which can then be
tracked and studied. Maps from TOPEX/Poseidon data help sailors and
commercial ships chart their courses. Offshore oil operators and cable-
laying vessels use knowledge of ocean circulation patterns to minimize
impacts from strong currents. Marine biologists use the data to monitor
and assess coral-reef ecosystems sensitive to ocean temperature
changes. The mission can even track ocean debris.

Jason, TOPEX/Poseidon’s follow-on, was launched December 7, 2001,
carrying updated versions of the same instruments. That joint U.S.-
French mission, which will continue building a long-term database, is
currently in a six-month scientific validation phase.

TOPEX/Poseidon’s longevity has given scientists the opportunity to fly
Jason in a parallel orbit, doubling the amount of data now being
collected. The tandem mission will enable improved detection of ocean
eddies, coastal tides and currents.

Planning for TOPEX/Poseidon began in 1979, when NASA started planning
the TOPEX mission, while the French Space Agency was planning Poseidon.
The two agencies formed a single mission in 1983.

JPL manages the U.S. portion of TOPEX/Poseidon and Jason for NASA’s
Earth Science Enterprise. JPL is a division of the California Institute
of Technology in Pasadena. Research on the Earth’s oceans using
TOPEX/Poseidon and Jason and other space-based capabilities is
conducted by NASA’s Earth Science Enterprise to better understand and
protect our home planet.

For more information on TOPEX/Poseidon and Jason, see: