2026-09-20T08:51:53Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/49600 2023-07-11 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

Kamalabadi, Farzad Landin, Kirk 2014-05-30T16:51:51Z 2014-05-30T16:51:51Z 2014-05 2014-05-30T16:51:51Z 2014-05 Local depletions in the equatorial ionospheric electron density, known as spread-F events, have been an active area of scientific research in the last decades. These are of special interest to the research community because of their potentially deleterious impact on trans-ionospheric communication links and navigation systems. The impetus for focused modeling and experimentation is the ultimate goal of predicting these events and subsequent mitigation of their negative impacts. A promising technique for direct imaging of these irregularities is based on a combination of satellite-borne and ground instruments, together with tomographic inversion techniques, to obtain multi-dimensional images of the ionospheric electron density. However, the inverse problem has some noted challenges due to inherent constraints on the acquisition geometry. One such system is based on coherent VHF and UHF transmission of radio signals by the Coherent Electromagnetic Radio Tomography (CERTO) beacons on board the Communications/Navigation Outage Forecasting System (C/NOFS) satellite, measured by a ground array of receivers located in a near-horizontal line around -12 degrees latitude. The resulting signals yield a set of electron density projections, known as the Total Electron Content (TEC), which can subsequently be used to produce two-dimensional images of ionospheric irregularities. The inherently exotic sampling geometry yields an under-determined, limited-angle tomography problem making it difficult to reconstruct accurate vertical variations in electron density. Moreover, the non-uniform sampling dictated by the acquisition geometry demands rigorous quantification of the information content in the reconstructed images. In the present work, we develop algorithms optimized for reconstructing ionospheric images containing such irregularities and apply them to experimental data to illustrate the capability and limitations of this approach for experimental investigation of this ionospheric phenomenon. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2014-04-22T14:57:06Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Landin_Kirk.pdf: 1108634 bytes, checksum: f526f5b96648a89f7f34ebe2a8d2b5cd (MD5) Made available in DSpace on 2014-05-30T16:51:51Z (GMT). No. of bitstreams: 2 Kirk_Landin.pdf: 1108634 bytes, checksum: f526f5b96648a89f7f34ebe2a8d2b5cd (MD5) license.txt: 4061 bytes, checksum: f6b8e2bf70e2c66e8ea6058963751254 (MD5) http://hdl.handle.net/2142/49600 en Copyright 2014 Kirk Landin tomography tomographic inversion limited-angle tomography ionosphere ionosphere irregularity plasma spread-f Communications/Navigation Outage Forecasting System (C/NOFS) C/NOFS satellite Coherent Electromagnetic Radio Tomography (CERTO) radio beacon radio beacon imaging occulation scintillation 2-D radio imaging of equatorial ionospheric plasma depletions with the C/NOFS satellite: algorithms and results text Electrical & Computer Eng 1933 Electrical & Computer Engr 1200 University of Illinois at Urbana-Champaign Thesis M.S. MS:Electr & Computer Eng-UIUC 10KS1200MS