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Ocean Surface Topography from Space
An Altimetry Milestone 3rd Anniversary OSTM/Jason-2 Completes Prime Mission
June 16, 2011

This June marks the third anniversary of the launch of the Ocean Surface Topography Mission on the Jason-2 satellite (OSTM/Jason-2). It's not just any anniversary: On June 20, 2011 the mission reaches an important milestone - the close of the prime mission. Having accomplished the principal mission goals -- as defined by the four mission partners: EUMETSAT, NOAA, CNES and NASA/JPL -- the spacecraft now enters its extended mission phase. The OSTM/Jason-2 instruments began cycle 1 of data collection on July 12, 2008, and by June 20, 2011, the satellite will have completed more than 14,000 orbits.

Jason-2 is the continuation of an important US/European satellite series that has now been providing vital data on sea level rise and ocean circulation for almost 19 years. This series of satellite radar altimeters measures the peaks and troughs of the sea surface height, or surface topography of the world's ice-free oceans every 10 days. The data time series began in 1992 with the launch of TOPEX/Poseidon, followed by Jason-1 in 2001. These important missions have provided researchers and society with a rich legacy of unprecedented ocean observations. Earth's ocean exerts a powerful influence on global climate, and never before have we had such accurate observations of the rate of sea level rise and the change of ocean circulation over time, an important indicator of climate change.

The many significant scientific outcomes from these data include:

  • Measuring global sea level rise

    Measuring global sea level rise

  • Mapping regional sea level variations

    Mapping regional sea level variations

    [image credit: CNES/LEGOS/CLS]

  • Improving ocean tide models

    Improving ocean tide models

    [image credit: R. Ray, GSFC]

  • Tsunami research

    Tsunami research

    [Image credit: T. Song, JPL]

    The figures on the left show observations by the NASA/CNES Jason-1 and Jason-2 satellites as they passed over the ocean tsunami waves generated by the magnitude 9.0 earthquake on March 11, 2011 off the coast of Japan. The graphs on the right show the satellite-observed tsunami height data (red and pink lines) confirmed by JPL's computer model prediction (black lines) based on GPS measurements. Jason-1 passed over the tsunami 7:30 hours after the earthquake and 'saw' a large wave. Jason-2 passed over the region 8:20 hours after the earthquake and 'saw' a smaller wave. The satellites cannot change their orbits or be directed to observe specific events like this, but may, by chance, measure them.

  • Benefits to society

    Benefits to society

Ocean altimetry satellites provide researchers and operational users, such as NOAA's extreme weather units, with valuable information about ocean circulation, ocean dynamics, sea level rise, and hurricane intensities. Data and images are available in near real-time for some uses, and are used for a wide range of scientific as well as commercial and practical applications.

Around the globe, operational weather agencies use Jason-2 data for climate forecasting. For many countries, these forecasts are crucial in planning for floods and drought, agricultural strategies and allocating water and energy use.

Jason-2 has been operating in a tandem mission mode with Jason-1 since February 2009. All spacecraft systems and instruments onboard Jason-2 continue to operate well. The mission teams and data users worldwide are looking forward to many future anniversaries.

In a cooperation between NASA, CNES, Eumetsat and NOAA, Jason-3, scheduled to launch in 2013, will continue this important time series following the legacy of TOPEX/Poseidon, Jason-1 and Jason-2. It will carry the same suite of instruments as its predecessors for obtaining high-precision sea surface height measurements.

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