(Credits NASA)
Satellite Skylab
Launched May 1973
Mission acquiring new knowledge in Space to improve life on Earth
Altitude 435 km
Inclination 50°
Skylab, America’s first experimental Space station, was launched in May 1973 and visited by crews three times in 1973 and 1974. It carried a generalised general active and passive microwave measurement system called S193. This instrument carried the first spaceborne altimeter, for the purpose of “to provideproviding ocean state effects on pulse characteristics.” Using a pulse width of 0.1 microseconds this system was able to get achieve a resolution of 15 m. It only operated over short orbital segments only but was able to demonstrate the measurement of coarse features of the marine geoid, such as major ocean trenches.

Further information on NASA/KSC website