The KT-19 Skin Surface Temperature Sensor (KSSTS) is an airborne radiometer that measures the brightness temperature of the surface beneath an aircraft. The instrument was used in NASA's Operation IceBridge over polar regions. By knowing the emissivity of the target—sea ice has an emissivity very close to one—KT-19 data were used to estimate the surface temperature. Thick sea ice is sometimes as cold as -20° or -30° Celsius (-4° or -22° Fahrenheit) while open water is around -2° Celsius (28° Fahrenheit). 

The KT-19 as calibrated for NASA’s IceBridge mission accurately measured the temperature of sea ice leads larger than 40 meters (130 feet). For larger leads covered in thin ice, the KT-19 provided surface temperature data that was used to estimate ice thickness.