期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
卷 119, 期 10, 页码 8648-8659出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2014JA020078
关键词
spaceborne SAR; ionospheric dispersion; ionospheric irregularity; triband path delay measurement; computerized ionospheric tomography
资金
- National Natural Science Foundation of China [61032009, 61372004]
- Fundamental Research Funds for the Central Universities
- International Science and Technology Cooperation Program of China [2011DFA22270]
- National Key Laboratory of Electromagnetic Environment
It is well known that the spaceborne synthetic aperture radar (SAR) at VHF-UHF band can be seriously affected by the ionosphere. Thus, the geophysical information of the ionosphere will be embedded in the low-frequency SAR echoes after they transverse the ionosphere. Correspondingly, the total electron content (TEC), a typical ionospheric information parameter, can be retrieved from the spaceborne SAR data. However, the existing dual-band techniques for TEC retrieval usually do not include consideration of multiple scattering effects caused by turbulent ionosphere, which plays an important role in the total path delay of signal under the strong fluctuation regimes. The result of TEC retrieval is therefore inaccurate and not applicable. Aiming at this issue, first, this paper analyzes the effects of regular background and the irregularity of electron density on SAR at L-band, and the theoretical formulation is given. Then, a triband path delay technique of TEC retrieval based on the SAR data is proposed. By using three path delays corresponding to three specific frequencies within the signal bandwidth, this technique can remove the errors of multiple scattering due to the irregularity, and a high accuracy resolution of TEC value therefore can be obtained. Meanwhile, the sensitivity of this technique is analyzed. Finally, compared with traditional dual-band technique, the numerical simulations show that the correction of SAR imaging based on triband technique is improved significantly. In addition, the resolution of reconstruction imaging using computerized ionospheric tomography performs significantly better based on the triband technique.
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