Inversion of Arecibo incoherent scatter radar coded long pulse backscatter spectra
Wu, Yulun
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https://hdl.handle.net/2142/108203
Description
Title
Inversion of Arecibo incoherent scatter radar coded long pulse backscatter spectra
Author(s)
Wu, Yulun
Issue Date
2020-05-15
Director of Research (if dissertation) or Advisor (if thesis)
Kudeki, Erhan
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Incoherent scatter radar
inversion
signal processing
Abstract
Incoherent scatter radar (ISR) at Arecibo Observatory measures the scattering of electromagnetic waves from random density fluctuations of ionospheric plasma particles (electrons and ions). Information about particle temperatures, ion concentrations, and Doppler shifts caused by particle motions can be estimated by inverting the power spectra of received scatter signals to the numerially implemented ISR forward spectral model in the frequency domain. Power spectrum estimates are derived by taking FFT of signal samples and averaging the magnitude square of the FFTs. Power spectra include both statistical estimation errors due to the use of finite length data sets and a characteristic shape that depends on ionospheric parameters via a known non-linear relationship that is exploited during the inversion process. This thesis first describes the numerical implementation of the complete collisional ISR spectral model using chirp-z algorithm, and mainly focuses on Arecibo coded long pulse (CLP) data analysis, including spectrum generation and inversion of raw voltage data from two receivers of Arecibo Observatory. Regular FFT method and the multi-level chirp-z algorithm for speeding up spectrum computation are presented. Weighted least-square spectrum inversion of the spectral estimates to double-humped spectral model of ionospheric incoherent scatter signals using various inversion techniques including the inversion of ion drift velocity using measured spectra ACF are discussed.
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