TerraRad's Technology

The TerraRad Tech L-band radiometer is based on space technology from Earth Observation satellites. The European Space Agency (ESA) Soil Moisture and Ocean Salinty (SMOS) and the NASA Soil Moisture Active Passive (SMAP) satellites use the same passive remote sensing technique for global climate and hydrology monitoring. Some of the unique aspects of our technology are…

Patented low mass and compact antenna enables precision drone-based radiometer


Operates in the internationally protected radiofrequency band at 1400 MHz to avoId interference


Unique calibration technique enables extremely low power consumption

Dual polarization instrument enables use of retrieval algorithms developed by NASA and ESA

Microwaves have a significantly longer wavelength than infrared or visible light, which enables these sensors to see through, and into, the earth’s surface. A radiometer is an instrument that measures naturally emitted radiation of very low power levels, similar to a thermal camera, but at a much longer wavelength. The TerraRad Portable L-band Radiometer, or PoLRa, uses a portion of the electromagnetic spectrum reserved only for these passive measurements between 1400 and 1426 MHz.

The earth’s surface emits microwaves as a function of its temperature, and its surface and material properties. The sun appears yellow because its 5700 K temperature causes its emission to peak near 600 nm, the wavelength of visible yellow light.

Passive microwave remote sensing is another name for the use of microwave radiometers. This technology relies on the fact that many environmental parameters  (i.e. soil and vegetation moisture) also alter the microwave signature of these natural materials. Water increases soil’s reflectivity and thus increases the contribution of “cold” space measured at the antenna.

By measuring the microwave power entering the antenna at two independent polarizations, we calculate the L-band Vegetation Optical Depth (L-VOD) and soil moisture. L-VOD is known to be proportional to crop yield (surface biomass) and to vegetation water content.

The penetration depth of L-band microwaves in soil is between 5 and 10 cm depending on its moisture content. Microwave radiometry is the only remote sensing technique capable of measuring subsurface properties and through thick vegetation.  

Portable L-Band Radiometer: Design and characterization

Published details on the hardware and calibration

The unique and patented dual-polarization antenna array provides two simultaneous and independent measurements. TerraRad’s Portable L-band Radiometer (PoLRa) can be mounted on a UAV (drone), vehicle, or installed on a tower or pole. 

The extremely low power consumption (< 5 W) enables the ground-based PoLRa to operate on solar power in remote locations. Use cases of remote ground-based PoLRa systems include Automatic Weather Stations (AWS) and soil moisture ground validation sites.

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