NASA Spinoff

Compact Radiometers Expand Climate Knowledge

According to the University of Melbourne, PLMR enables mapping in unprecedented detail of soil moisture, land surface salinity and temperature, and ocean surface salinity and temperature. The University appreciates the instrument’s small size, light weight, and affordability.


Based on the advances made possible by working with NASA, ProSensing offers two lightweight radiometers for mapping soil moisture, ocean salinity, and wind speed: the PLMR and the Scanning Low Frequency Microwave Radiometer. ProSensing’s customers include government research agencies, university research groups, and large corporations in North America, Europe, and Asia.

altThe way a microwave radiometer works is by measuring natural radiation. In the case of the ocean, the amount of signal that is radiated changes with salinity. The parameter used to describe this is called the emissivity of the surface. In the case of soil, the emissivity changes with moisture. Additionally, the emissivity depends on how rough a surface is, and this is why a radiometer can also measure wind speed over the ocean. The faster the wind blows, the rougher the surface gets, resulting in more signals being transmitted to the radiometer.

In 2008, the NASA-derived technology influenced the design and development of a hurricane imaging radiometer (HIRAD) to measure ocean wind speed in hurricanes. The instrument, under development at Marshall Space Flight Center, uses the same technique as the ultrastable radiometer, but operates at a different wavelength.

altHIRAD is a compact, lightweight, low-power instrument that produces imagery from an aircraft or spacecraft. Specifically, Marshall is developing HIRAD to measure ocean surface wind speed from hurricane reconnaissance aircraft with fine spatial resolution over a wide angular swath. ProSensing delivered 12 single-board, four channel radiometer receivers to Marshall, which are now being integrated into HIRAD.

In 2009, ProSensing received a contract from one of the largest research centers in Germany, the Institute of Chemistry and Dynamics of the Geosphere, to build a copy of the PLMR. Requiring six ultrastable radiometer modules, the Institute uses PLMR for research measurements of soil moisture and salinity.

Most recently, the University of Massachusetts requested two radiometer modules from ProSensing to test their applicability for noninvasive readings of cerebrospinal fluid temperature (temperature of the fluid that circulates around and through the brain and spinal cord). Usually, a spinal tap is used for this procedure to diagnose certain neurologic disorders, particularly infections like meningitis. “If you can take temperature remotely with a radiometer and see that it is elevated, then this could have wide application in emergency rooms,” says Mead.

Mead says many projects have grown out of the NASA SBIR program over the years. “NASA had a long-term interest in developing the technology and was eager to take what we built and put it to use. That gave us something to design to. Now we have some fairly mature projects, and some that are just getting kicked off.”