Altimetry was announced as a priority at the Williamstown Symposium in 1969. The 1970s saw the development of accurate satellite altimeter systems, with Skylab (which produced the first measurements of undulations in the marine geoid due to seafloor features), GEOS-3 and Seasat, whose data were widely and freely distributed to scientists throughout the world, laying the foundations for a new generation of ocean satellites. In the 1980s, only Geosat was launched, whose data was at first classified.
In the 1990s, with ERS-1 and Topex/Poseidon, altimetry began providing vital information to a growing international user community (more than 1,000 teams of users around the world in 2006). In the 2000s, more than a breakthrough in ocean observation, Jason-1 and Envisat opened a new pathway for radar altimetry, and it has helped to build up a 20-year time series of continuous sea-surface measurements.
- The first altimetric satellites: Skylab, GEOS 3, Seasat