The radar altimeter exploits sophisticated radar techniques for improved resolution and observing potential. The altimeter makes a measurement of the distance between the satellite and the surface. However, this measurement cannot be converted into the more useful measure of the height of the surface until the satellite’s position is accurately known.

The satellite therefore carries three startrackers for measuring the exact direction to the spot on the surface where the measurement is made, so that it can be precisely located. In addition, a radio receiver called Doppler Orbit and Radio Positioning Integration by Satellite (DORIS) and a small laser retroreflector ensure that the satellite’s position is accurately tracked.

Credits: ESA - AOES Medialab