電離層斷層掃描之研究

computerized ionosphere tomography

宋昆霖(Kun-lin Sung)

指導教授 ： 陳念偉

國立中央大學/資訊電機學院/電機工程學系/碩士(2007年)

摘要

傳統電離層觀測技術，如電離層雷達（Ionosonde）、非同調散射雷達（Incoherent Scattering Radar, ISR）觀測技術，僅能獲得雷達本地上空之電離層電子濃度資訊。相較而言，電離層斷層掃描技術(Ionospheric Tomography)可經由衛星與全球地面接收站之電波訊號，探測較大尺度及多維度之電離層結構。本論文對常用之斷層掃描演算法(algorithm)，代數演算法(algebraic reconstruction techniques, ART)、倍數代數演算法(multiplicative algebraic reconstruction techniques, MART)、以及同步迭代演算法(simultaneous iterations reconstruction technique, SIRT)，透過對數個典型之電離層電子濃度分佈場景(scenario)進行有系統的參數分析(parametric study)，以期瞭解各演算法中參數設定對反衍結果之影響，進而一窺各演算法之特性及其適用之反衍結構，此研究對於實際電離層觀測資料反衍時演算法選取將有很大的助益。

關鍵字

電離層 ； 斷層掃描 ； 電離層斷層掃描

並列摘要

The parametric study of the traditionally-used algorithms, viz. algebraic reconstruction technique (ART), multiplicative algebraic reconstruction technique (MART), and simultaneous iterations reconstruction technique (SIRT), for computerized ionosphere tomography (CIT) is presented in this thesis. Also, the study of incorporation of the horizontal integration paths into the retrieval to alleviate the issue on retrieving multi-layered ionosphere structures is demonstrated. Specifically, each of the three algorithms is applied to retrieve the electron density of several scenarios, which mimic the classical irregularities in the Earth’s ionosphere. The impact of the parameters associated with each algorithm on the retrieval results is investigated on a case-by-case manner. Technically speaking, the MART and SIRT are more suitable for CIT as they are essentially case independent. Indeed, the MART promises no artifacts in the retrieved images and a relatively good similarity to the proposed scenarios, whereas the SIRT obtains relatively accurate calculation in the vertical total electron content. This study provides a better understanding of the CIT algorithms as well as directions to develop the avenues for further improvement on the algorithms.

並列關鍵字

tomography ； algorithm ； Ionospheric Tomography

參考文獻

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