Fundamentals of Radar Altimeters

Altimeter fundamentals

Three basic measurements, all over the oceans:

Geoid height: measure time of travel (actually the TWTT, two way travel down, down for the satellite to the sea surface and then back up), and use speed of light to get distance from satellite, whose orbit is known. This is generally expressed as an anomaly above or below the ellipsoid.
SWH (Significant wave height): Measure duration of return: if  short, sea state is low and all energy comes back at the same time.

This is somewhat noisy because it takes 10 days to collect, but shows the largest waves in the southern ocean driven by the West Wind Drift.
Wind speed: Measure strength of return (backscattered power): strong return if low wind; as wind increases, the roughness of the sea surface increases, and less energy is returned because it is reflected in other directions.

This is somewhat noisy because it takes 10 days to collect, but shows the southern ocean and the West Wind Drift.

Marine geoid

Temporary disturbances of sea level include:

Average many orbits to get geoid, which removes weather and ocean currents.

Subtract average to get oceanographic features like eddies and the wall of the Gulf Stream


Last revision 8/23/2016