Inside the Microwave Radiometer Aboard NASA's Soil Moisture Active Passive Satellite

The microwave radiometer on NASA's Soil Moisture Active Passive (SMAP) satellite was designed and built at NASA's Goddard Space Flight Center. Along with the microwave radar, data from the radiometer will be used to calculate the water content of Earth's soil. Instrument Scientist Jeff Piepmeier explains the technology that Goddard incorporated in the radiometer. All types of soil emit microwave radiation, but the amount of water changes how much of this energy is emitted. The drier the soil, the more microwave energy; the wetter the soil, the less energy. But radio frequency interference is a problem, even though the instrument is passively listening in a region of the microwave spectrum where transmission is prohibited. Some of the signals from the surrounding regions leak into the protected 'listen-only' band. Goddard engineers developed new hardware and software to search for and cut out the erroneous measurements.