PROJECT TITLE :

The Impact of System Effects on Estimates of Faraday Rotation From Synthetic Aperture Radar Measurements

ABSTRACT:

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 simply corrected given estimates of the Faraday rotation angle, i.e., $Omega$. Many strategies to derive $Omega$ from polarimetric measurements are known, however they are stricken by system distortions (crosstalk and channel imbalance) and noise. A 1st-order analysis for the most robust Faraday rotation estimator results in a differentiable expression for the bias in the estimate of $Omega$ in terms of the amplitudes and phases of the distortion terms and also the covariance properties of the target. The analysis applies equally to L-band and P-band. We have a tendency to derive conditions on the amplitudes and phases of the distortion terms that yield the maximum bias and a compact expression for its worth for the vital case where $Omega=zero$. Actual 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 utmost bias is shown to be insensitive to the amplitude of the channel imbalance terms. These results are necessary not simply for correcting polarimetric data but additionally for assessing the accuracy of the estimates of the overall electron content derived from Faraday rotation.