The Soil Moisture Active Passive (SMAP) "Faraday Rotation Angle (L1, Passive, Fore)" layer displays Faraday rotation angle in degrees for the fore and aft scan of the SMAP radiometer. Faraday rotation is a phenomenon in which the polarization vector of an electromagnetic wave rotates as the wave propagates through the ionosphere. While the Faraday rotation is minimized by SMAP’s 6:00 a.m./6:00 p.m. near sun-synchronous orbit, the inclusion of this information provides a capability to correct for possible Faraday rotation.

The SMAP spacecraft carries two instruments, a radar (active) and a radiometer (passive), that together make global measurements of land surface soil moisture and freeze/thaw state. It is useful for monitoring and predicting natural hazards such as floods and droughts, understanding the linkages between Earth’s water, energy and carbon cycles, and reducing uncertainties in predicting weather and climate.

References: SMAP L1B Radiometer Half-Orbit Time-Ordered Brightness Temperatures

Data field: faraday_rotation_angle