Mass: 2,300 kilograms (5,070 pounds)
Science instruments: Radar altimeter, scanning multichannel microwave radiometer,
microwave scatterometer, imaging radar, visual and infrared radiometer
In the 1970s, JPL engineers and scientists realized that the sensors they were
developing for interplanetary missions could be turned upon Earth itself to better
understand our home planet. In 1978, JPL built an experimental satellite called Seasat
to test a variety of oceanographic sensors including imaging radar, altimeters,
radiometers and scatterometers.
Seasat flight-tested four instruments that used radar to study Earth and its seas.
Radars are useful tools because they can penetrate clouds, they operate in all weather
conditions, and they provide their own illumination so they can function day and night.
The radar instruments on Seasat measured the satellite's distance from the sea surface,
measured near-surface ocean winds and took pictures using radar rather than light
for illumination. Seasat also carried a visual and infrared radiometer that provided
measurements that were used to judge the results of the radar instruments.
Seasat was launched on June 26, 1978, on an Atlas Agena rocket from Vandenberg
Air Force Base, California. Unlike launches of interplanetary spacecraft from
Florida on eastward flight paths, launches from Vandenburg place the satellite in a north-south
orbit that takes it close to Earth's poles. Seasat sent data to Earth for 106 days.
Many later Earth-orbiting instruments developed at JPL owe their legacy to the Seasat
mission. These include imaging radars flown on NASA's Space Shuttle as well as such
Earth-orbiting satellites and instruments as Topex/Poseidon, the NASA Scatterometer
(NSCAT), QuikScat and the planned Jason 1.