K-Band Radiometer

A K-band radiometer is a passive microwave sensor working near 18 to 27 GHz, used on altimetry missions to measure the wet tropospheric path delay. Water vapor and cloud liquid emit in this band, so brightness temperatures at channels around 18, 21, and 34 GHz retrieve the column water vapor that slows the altimeter’s radar pulse, a correction worth tens of centimeters in sea surface height. The Advanced Microwave Radiometer on Jason and Sentinel-6 is the working example. Without it the altimeter range would carry an uncorrected, weather-dependent bias far larger than the few-centimeter accuracy the mission targets.