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Seasat's synthetic aperture radar antenna being unfolded from launch configuration to its full size.
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Artist’s concept of Seasat.
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In 1978, JPL flew the world's first dedicated oceanographic satellite, Seasat-A. Oceanographers wanted measurements from space that could help them understand how Earth's oceans circulate. They had tried to measure ocean currents from ships for decades, but because ships move slowly, and can only measure a tiny portion of the ocean at a time, they weren't good platforms for this kind of research. Satellites, which could see large swaths of Earth at once, promised to be much better.
Seasat-A was a low-cost, 'proof of concept' mission that carried one infrared and four microwave instruments. The mission measured wind speed, height and temperature at the ocean surface.
Seasat-A also carried a synthetic aperture radar, which produced images of the ocean and land surface. This instrument proved that sub-surface waves exist in the oceans, and revealed images of features buried under desert sands. These findings inspired a series of Space Shuttle-based successors that flew in 1981, 1984, 1994 and 2000. The final mission in 2000, known as the Shuttle Radar Topography Mission, produced a digital elevation map of 80 percent of Earth's land area.
Seasat itself, however, failed after only 90 days in orbit. NASA's investigation of the failure led it to the satellite contractor, Lockheed, which had installed a bad power coupling on the satellite's solar panels. Nonetheless, Seasat demonstrated that ocean remote sensing could produce meaningful scientific results. |
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