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Low-Cost High Frequency Passive Microwave Radiometer for Ground Measurements


Passive microwave sensors are key sensor payloads on many operational satellites, including those operated by NOAA and EUMETSAT – the Advanced Microwave Sounding Unit (AMSU) and the Microwave Humidity Sounder (MHS).  Over the past decade, satellite-based high frequency measurements at and above 150 GHz (including those near the 183 GHz water vapor absorption band) have become extremely useful for the retrieval of several parameters, including precipitation rate and snowpack properties.  In order to advance our understanding of the relationship between these parameters and the emitting microwave energy (and to advance radiative transfer model development), a sensor that can be used on the ground (either pointing upward or downward) which takes measurements at these high frequencies needs to be developed – presently, such sensors typically make measurements at 90 GHz or lower. 


Project Goals:  It is envisioned that the prototype sensor would work off of the design of an existing instrument and potentially have a full complement of measurements spanning the range of 10 – 190 GHz (i.e., have channels that are comparable to existing or future planned microwave sensors such as the Advanced Technology Microwave Sounder (ATMS) and the GPM Microwave Imager (GMI)). As such, a prototype sensor is envisioned for Phase I whereas a fully operational instrument with the following attributes would be produced during Phase II:


(1)  Dual Polarization:  Ice crystals scatter and depolarize microwave radiation depending on particle size and observation frequency (Matzler, 1984; Hewison et al., 1999).  Emission and scattering of snow depends on depth, density, morphology and liquid water content.  Polarized microwave observations can provide this important information.

(2)  Upward- and downward-looking Mobility:  Upward for liquid cloud water path retrieval (for cloud and precipitation, downward for simultaneous cloud liquid water path and surface emissivity retrievals.

(3)  Scanning ability:  Cross-track sensors such as AMSU, MHS and ATMS  view the earth at varying angles.


Phase I Activities and Expected Deliverables:

·         Prototype radiometer design and test data

·         Deliverable – Working model with at least some of the requested attributes


Phase II Activities and Expected Deliverables:

·         Development of full working radiometer with required measurement bands, polarizations, scanning geometry

·         Test data sets documenting instrument performance under a variety of meteorological and surface conditions

·         Deliverable – Fully functional instrument

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