期刊
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
卷 53, 期 8, 页码 4284-4298出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TGRS.2015.2395076
关键词
Calibration; Faraday rotation; ionospheric structure; radar imaging; radar polarimetry
类别
资金
- European Space Agency (ESA) under ESA/European Space Research and Technology Centre (ESTEC) [22849/09/NL/JA/ef]
- U.K. National Environment Research Council through the National Centre for Earth Observation
- U.K. Space Agency
- NERC [nceo020005] Funding Source: UKRI
- Natural Environment Research Council [nceo020005, NE/D000874/1] Funding Source: researchfish
Radio waves traversing the Earth's ionosphere suffer from Faraday rotation with noticeable effects on measurements from lower frequency space-based radars, but these effects can be easily corrected given estimates of the Faraday rotation angle, i.e., O. Several methods to derive O from polarimetric measurements are known, but they are affected by system distortions (crosstalk and channel imbalance) and noise. A first-order analysis for the most robust Faraday rotation estimator leads to a differentiable expression for the bias in the estimate of O in terms of the amplitudes and phases of the distortion terms and the covariance properties of the target. The analysis applies equally to L-band and P-band. We derive conditions on the amplitudes and phases of the distortion terms that yield the maximum bias and a compact expression for its value for the important case where Omega = 0. Exact simulations confirm the accuracy of the first-order analysis and verify its predictions. Conditions on the distortion amplitudes that yield a given maximum bias are derived numerically, and the maximum bias is shown to be insensitive to the amplitude of the channel imbalance terms. These results are important not just for correcting polarimetric data but also for assessing the accuracy of the estimates of the total electron content derived from Faraday rotation.
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