Seasat was the first satellite dedicated to studying Earth's oceans.
Illustration: NASA
1978: Seasat 1, the first satellite dedicated solely to oceanographic observation, is launched.
Seasat measures sea-surface temperatures and winds, wave heights, various ocean and sea-ice features, while monitoring other changes in the planet's physical geography, such as the polar ice caps. It provides 95 percent global coverage every 36 hours.
Seasat's payload includes a synthetic aperture radar for measuring wave action, as well as a radar altimeter and radiometer for tracking wind speed. The satellite was built by the Jet Propulsion Laboratory in Pasadena, California.
A short circuit almost four months after launch knocked out Seasat for a while in October 1978 but the satellite was repaired and remains in orbit. You can track the satellite's whereabouts here.