CAREER: Enabling the Next Generation Wideband Microwave Radiometers for the Remote Sensing of the Cryosphere

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Understanding the Cryosphere, Earth's surface covered by snow and ice, and predicting future changes in its ice volume and mass are critical to track the climate and the water cycle on our planet. Because of the extreme environmental conditions, high costs of sparse in-situ measurements, and concerns about increasing human footprint associated with these regions, remote sensing instruments are preferred to monitor the Cryosphere. Among these instruments, microwave radiometers, i.e., passive receivers measuring microwave radiations from their targets, have many advantages since they can provide data independent of cloud conditions and solar illumination, and their measurements are highly sensitive to important ice properties such as thickness, temperature, density, and grain size. Provided with enough bandwidth, these instruments are, hypothetically, capable of profiling these properties from the surface to the deep ice. However, radiometer operations to observe the Cryosphere are currently far from ideal. First, they are limited to a few narrow frequency bands to avoid interference from active sources such as radars and wireless communication systems. Second, the electrical properties of ice, which determine the amount of electromagnetic radiation it emits, are not fully characterized versus frequency and temperature. This CAREER research, by modeling the electrical properties of ice across wide ranges of frequencies and temperatures and developing efficient interference mitigation algorithms, will enable the next generation of microwave radiometers capable of utilizing wide microwave frequency bands to fully probe Earth's ice bodies. Furthermore, with an education plan integrated with the research activities, this project will grow the investigator as a prominent scientist-educator and provide an applied, hands-on electromagnetics training for students at his institution. Electromagnetic penetration depths vary with frequency in ice; thus, wideband microwave radiometers can be used to profile thermal and physical properties of ice bodies versus depth. The overarching goal of this career development project is to enable next generation of such instruments for the remote sensing of the Cryosphere. In pursuit of this goal, the complex permittivity of ice will be measured across wide frequency (0-50 GHz) and temperature (200-273 K) ranges for its electrical characterization. Measured permittivity values will be verified by comparing simulated microwave radiations over the Antarctic and the Arctic to the measurements of polar-orbiting space-borne microwave radiometers. Furthermore, multi-dimensional, machine learning based radio frequency interference detection and mitigation algorithms for microwave radiometers will be developed to allow their operations across wide frequency bands occupied and shared by active services. Lastly, a digital wideband radiometer prototype will be developed at the grantee's institution to implement these algorithms and validate the project outcomes through snow remote sensing measurements at fully characterized ground sites. The research activities will be incorporated into the engineering courses as a part of the investigator's applied electromagnetics education philosophy to educate future engineers and scientist in the field of microwave remote sensing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.