The NASA NSCAT and Topex/Poseidon programs

The National Aeronautics and Space Administration, in support of global oceanographic studies and the large-scale oceanographic experiments of the World Climate Research Program, has begun a program to measure oceanic winds, currents, and tides from space. The two major elements of the program are: (a) A Nasa Scatterometer NSCAT to measure winds from space to be flown on the Navy's Remote Ocean Sensing System NROSS satellite; and (b) the Topex/Poseidon altimetric satellite to measure currents and tides. The NSCAT will measure surface wind speed and direction on a 50 km grid with an accuracy of
\pm 2
m/s and
\pm 20\deg
along 600 km wide swaths on either side of the spacecraft to provide near global coverage every two clays for three years. NSCAT is funded and launch is planned for September 1990. The combination of Nasa's Topex program with the Poseidon program of the French Centre National d'Etudes Spatiales, Topex/Poseidon, has led to plans to launch a joint altimetric satellite in February 1991 to measure sea-surface topography with an accuracy of
\pm 14
cm and a precision of
\pm 2.4
cm along a fixed global grid every 10 days for three years. These measurements will be used to calculate the time-varying and permanent surface geostrophic currents at the sea surface, oceanic tides, and ocean wave height.