Platforms: TOPEX/POSEIDON

From

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.

Objectives

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

Mission

• 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

Spacecraft

• 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

Payload/Sensors

• 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

Data

• 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

Спутник

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

Результат

	This plot shows the mean wet troposphere correction during cycle 30 of the Topex/Poseidon mission, i.e. during the 10-day interval starting 7 July 1993. The mean correction during this time period was 156 mm, the maximum 454 mm, the minimum 0 mm.

Источники

Описание: http://sealevel.jpl.nasa.gov/missions/topex/
Изображения: http://space.skyrocket.de/doc_sdat/topex-poseidon.htm, http://iliad.gsfc.nasa.gov/opf/algorithms/wet_topex.html, http://en.wikipedia.org/wiki/TOPEX/Poseidon