More than 15 years of radar altimetry
It works simply by beaming down a signal that hits the ocean surface and then bounces back to an antenna. The distance (or range) from the ocean to the satellite is then calculated from the return-trip time of the signal.
Combined with ultra-precise positioning information, derived chiefly from the French Doris system, this range measurement is converted into sea-surface height.
In the 1970s, several satellites were launched to validate this radar altimetry concept, paving the way for future missions. In later years, with the launch of the European ERS-1 satellite in 1991 and especially the French-U.S. Topex/Poseidon satellite in 1992, satellite altimetry data completely transformed our understanding of the oceans and the currents driving them.
Seeing the oceans in a new light
Today, satellites are capable of measuring variations in sea-surface height with an accuracy of 2 cm.
Radar altimetry has enabled oceanographic research to make great strides. But according to some scientists at the symposium in Venice, Italy, its biggest contribution is to have changed the way scientists view the oceans.
Using these vital observations, oceanographers are highlighting very slow variation phenomena and what is increasingly clear is the way they interact with the atmosphere.
In the field of climate research, gaining a closer understanding of ocean/atmosphere interactions is a key challenge that lies ahead for scientists who, with other users, are demonstrating the huge benefits afforded by altimetry simply through its ability to measure distances from space.