Radar Altimetry

Radar altimetry is a satellite remote sensingRemote SensingRemote sensing is the science of collecting data about Earth's surface without direct physical contact, primarily usi... technique that measures the distance between the spacecraft and the Earth's surface by transmitting short radar pulses nadirNadirNadir is the point on Earth's surface directly below a satellite or airborne sensor. Images acquired at nadir have th...-ward and precisely timing their return. By combining the measured range with accurate knowledge of the satellite's orbital position, altimeters derive surface elevation with centimeter-level precision over oceans and decimeter-level over land and ice. How it worksA radar altimeter transmits microwave pulses (typically at 13.6 GHz Ku-band) that reflect off the surface and return to the satellite. The round-trip travel time, corrected for atmospheric delays, yields the range to the surface. The shape of the returned waveform provides information about surface roughness, wave height (over oceans), and ice sheet characteristics. Missions like Jason-3, Sentinel-6, and ICESat-2 (laser altimetry) provide global coverage. ApplicationsRadar altimetry is fundamental to monitoring global sea level rise, ocean circulation, and tsunami propagation. Over land, it measures river and lake water levels, ice sheet elevation changes, and terrain height. Altimetric sea surface height data has been continuously collected since 1992, providing a critical climate data record for tracking global sea level change. Radar altimetry provides one of the most important long-term records of global environmental change. Its continuous, precise measurements of sea level and ice sheet elevation are essential for understanding and responding to climate change.