2-D radio imaging of equatorial ionospheric plasma depletions with the C/NOFS satellite: algorithms and results

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

Landin, Kirk ; Kamalabadi ; Farzad

关键词: 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;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49600/Kirk_Landin.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Local depletions in the equatorial ionospheric electron density, known asspread-F events, have been an active area of scientific research in the lastdecades. These are of special interest to the research community because oftheir potentially deleterious impact on trans-ionospheric communication linksand navigation systems. The impetus for focused modeling and experimentation isthe ultimate goal of predicting these events and subsequent mitigation of theirnegative impacts.A promising technique for direct imaging of these irregularities is based on acombination of satellite-borne and ground instruments, together with tomographicinversion techniques, to obtain multi-dimensional images of the ionosphericelectron density.However, the inverse problem has some noted challenges due toinherent constraints on the acquisition geometry.One such system is based on coherent VHF and UHF transmission of radio signalsby the Coherent Electromagnetic Radio Tomography (CERTO) beacons on board theCommunications/Navigation Outage Forecasting System (C/NOFS) satellite, measuredby a ground array of receivers located in a near-horizontal line around -12degrees latitude.The resulting signals yield a set of electron densityprojections, known as the Total Electron Content (TEC), which can subsequentlybe 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 accuratevertical variations in electron density. Moreover, the non-uniform samplingdictated by the acquisition geometry demands rigorous quantification of theinformation content in the reconstructed images.In the present work, wedevelop algorithms optimized for reconstructing ionospheric images containingsuch irregularities and apply them to experimental data to illustrate thecapability and limitations of this approach for experimental investigation ofthis ionospheric phenomenon.