Date of Award

12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Aeronautics and Astronautics

Committee Chair

James L. Garrison

Committee Member 1

Arthur E. Frazho

Committee Member 2

Keith A. Cherkauer

Committee Member 3

Jeffrey R. Piepmeier

Abstract

The measurement of soil moisture is essential for studying the hydrological cycle. Passive microwave radiometry is the most mature technology for the remote sensing of soil moisture, as demonstrated on ESAs Soil Moisture and Ocean Salinity (SMOS) satellite and the Soil Moisture Active Passive (SMAP) mission from NASA. Global Navigation Satellite System-Reflectometry (GNSS-R) has been demonstrated as an alternative approach to the remote sensing of soil moisture, through several airborne and ground-based experiments. All of these systems operate in L-band (1575.42 MHz for GNSS) which has a penetration depth in soil of only a few cm. GNSS signals are also very weak, as compared to communication signals. In order to study the sensing of soil moisture at deeper penetration depth by using communication satellites Signals of Opportunity (SoOp), we selected the P-band signal (260 MHz) transmitted by UHF-Follow-On (UFO) geostationary satellite as the source for implementing reflectometry. we have deployed an experiment at the Agricultural Center for Research and Education (ACRE) at Purdue University and verified the spectrum of the signal collected by a hand-made Yagi antenna and software-defined-radio (SDR) with information published by amateur radio website. The reflectivity has retrieved from the autocorrelation of direct signal and correlation between the direct and reflected signals. Moreover, the channel gain and noise can be estimated by the extra calibration chain, the antenna gain and noise were obtained by the empirical model. A flight campaign was conducted to demonstrate this method various soil moisture conditions. To determine the requirement of airborne equipment, we conducted a simulator with Matlab to evaluate the performance under different scenarios including the ideal setting, and using actual geospatial information from past flights of the aircraft. The sensitivity of reflectivity was studied by perturbing the calibrating parameters , The flight campaign was accomplished in Little Washita, Oklahoma, in the October 2016, and the coverage includes the land and Lake Ellsworth as a calibration source. The Agriculture Research Service (ARS) Micronet provides the temperature and soil moisture at depths of 5, 25, and 45 cm by a network of 52 observation stations every 5 minutes, and reflectivities of sites can be calculated by the empirical model with soil moisture, temperature, soil texture, etc. According to the initial results from the flight campaign, the change of reflectivity due to the transition between the land and lake is obvious, and the estimates of reflectivity are evidently high for certain locations with high reflection like water reservoir and rivers.

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