DC-3
Douglas DC-3

The Passive Active L- and S-band Sensor (PALS) is a combined airborne polarimetric radiometer and radar developed by NASA’s Jet Propulsion Laboratory (JPL). It was designed to evaluate the benefits of combining remote passive and active sensors for ocean salinity and soil moisture measurements. Both the radiometer and radar within PALS operate across the L- (1.41 GHz, 1.26 GHz) and S-band (2.69 GHz, 3.15 GHz) frequencies to measure brightness temperature and radar backscatter of ocean salinity and soil moisture. PALS has a spatial resolution ranging from 600 to 1500 m depending on the altitude of the aircraft. PALS can be equipped on many different aircraft due to its design and is typically used for validation of Aquarius and SMAP satellite observations.