| Abstract: |
Mark J. Andrews, Oguz Demir (presenter: demir.15@osu.edu), Alexandra Bringer, Joel T. Johnson, Kenneth C. Jezek1
ElectroScience Laboratory, The Ohio State University, Columbus, OH
1 Byrd Polar Research Center, The Ohio State University, Columbus, OH
The Ultra-Wideband Software-Defined Microwave Radiometer (UWBRAD) was developed under the support of NASA’s Instrument Incubator Program to measure Earth brightness temperatures in the range 500-2000 MHz. UWBRAD is a “pseudo-correlation” radiometer design that includes a common 0.5-2 GHz front end used to create twelve 100 MHz channels with center frequencies ranging from 540 MHz to 1980 MHz. Each channel is fully digitized and processed in real time for identification and mitigation of radio frequency interference. The instrument has, through lab tests and field campaigns, proved its capability in making accurate measurements over the desired band of operation in the presence of RFI, including a past deployment to observe the Greenland ice sheet in September 2016.
UWBRAD’s calibration and RFI processing steps are performed in three stages. The first uses data recorded at 1 msec time resolution to perform pulsed RFI detection and removal, resulting in a 100 msec integrated product when completed. The second then calibrates the data into antenna temperatures using internal calibration source measurements, and performs cross-frequency RFI detection removal as well as other RFI processing steps. The final step uses observations of sea scenes to correct for antenna effects to reach calibrated brightness temperatures. This final step requires a model for thermal emission from the sea surface from 500-2000 MHz.
A second airborne campaign over the Greenland ice sheet was accomplished in September 2017. In preparation for this campaign, further tests of the instrument thermal stability and calibration properties were conducted. Instrument modifications were also performed to address potential failure mechanisms in the presence of high amplitude RFI signals. Results from these pre-campaign tests will be described in the presentation, along with the associated results and calibration tests conducted during the campaign. The three UWBRAD calibration steps will also be described in detail, along with information on the sea surface model applied and the RFI information observed at each stage.
Properties of the resulting brightness temperature spectra will also be reported, including observations of boreal land, sea surface, and ice sheet scenes. Implications of these results for the continued use of ultra-wideband UHF microwave radiometry for Earth remote sensing will also be summarized.
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