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Launched in 1992, TOPEX/Poseidon is a joint venture between CNES and NASA that measured ocean surface topography to an accuracy of 4.2 cm, enabled scientists to forecast the 1997-1998 El Nino, and improved understanding of ocean circulation and its effect of global climate. While a 3-year prime mission was planned, with a 5-year store of expendables, TOPEX/Poseidon delivered an astonishing 13+ years of data from orbit. The mission ended in January 2006.

In those 13 years, it:

  • Measured sea levels with unprecedented accuracy to better than 5 cm
  • Continuously observed global ocean topography
  • Monitored effects of currents on global climate change and produced the first global views of seasonal changes of currents
  • Monitored large-scale ocean features like Rossby and Kelvin waves and studied such phenomena as El Nino, La Nina, and the Pacific Decadal Oscillation
  • Mapped basin-wide current variations and provided global data to validate models of ocean circulation
  • Mapped year-to-year changes in heat stored in the upper ocean
  • Produced the most accurate global maps of tides ever
  • Improved our knowledge of Earth's gravity field


  • Three-year global view of Earth's oceans
  • Improved understanding of ocean currents
  • Improved forecasting of global climate


  • Joint NASA-CNES program
  • Launched August 10, 1992
  • Launch Vehicle: Arianespace's Ariane 42P
  • Launch Site: Centre Spatial Guyanais, Kourou, French Guiana
  • Operations for 3-year prime mission, 6-year extended: JPL
  • Orbit: 1336-km, circular, 66° inclination
  • 10-day repeat of ground track (±1-km accuracy)
  • Covers 95% of ice-free oceans every 10-days


  • Based on Fairchild's Multi-Mission Spacecraft bus
  • Total mass: 2402 kg (5296 lbs)
  • Single solar panel provides 3.4 kW of power
  • 1.2 m (4 foot) high-gain antenna communicates through TDRSS
  • Reaction wheels and torque rods maintain 3-axis stabilization and nadir pointing
  • Hydrazine propellant system provides orbital maintenance


  • NASA dual-frequency (C- and Ku-band) altimeter and CNES single-frequency (Ku-band) solid-state altimeter measures height above sea
  • NASA microwave radiometer measures water vapor along altimeter path to correct for pulse delay
  • NASA Global Positioning System demonstration receiver provides precise orbit ephemeris data
  • NASA laser retroreflector array works with ground stations to track satellite and calibrate and verify altimeter measurements.
  • CNES DORIS Doppler tracking antenna receives ground signals for precise orbit determination, satellite tracking, and ionospheric correction data for CNES altimeter


  • Sea-level measurement accuracy 4.2 cm (1.7 inch)
  • Data coverage global between 66°N and 66°S latitude
  • Data availability through NASA/JPL and CNES

Источник: JPL.NOAA

Изображения: space.skyrocket.de, NASA, Wikipedia