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

Article English OPEN
Quegan, S. ; Lomas, M.R. (2015)
  • Publisher: Institute of Electrical and Electronics Engineers

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., Ω. Several methods to derive Ω 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 Ω 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 Ω = 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.
  • References (29)
    29 references, page 1 of 3

    [1] M. P. M. Hall, L. W. Barclay, and M. T. Hewitt, Eds. Propagation of Radiowaves. London, U.K.: The Institution of Electrical Engineers, 1996.

    [2] P. A. Wright, S. Quegan, N. S. Wheadon, and C. D. Hall, “Faraday rotation effects on L-band spaceborne SAR data,” IEEE Trans. Geosci. Remote Sens., vol. 41, no. 12, pp. 2735-2744, Dec. 2003.

    [3] A. Freeman and S. S. Saatchi, “On the detection of Faraday rotation in linearly polarized L-band SAR backscatter signatures,” IEEE Trans. Geosci. Remote Sens., vol. 42, no. 8, pp. 1607-1616, Aug. 2004.

    [4] S. Quegan et al., Report for Mission Selection: Biomass, Eur. Space Agency, Noordwijk, The Netherlands, ESA SP 1324/1 (vol. 3), 2012.

    [5] S. H. Bickel and R. H. T. Bates, “Effects of magneto-ionic propagation on the polarization scattering matrix,” Proc. IRE, vol. 53, no. 8, pp. 1089-1091, Aug. 1965.

    [6] A. Freeman, “Calibration of linearly polarized polarimetric SAR data subject to Faraday rotation,” IEEE Trans. Geosci. Remote Sens., vol. 42, no. 8, pp. 1617-1624, Aug. 2004.

    [7] R.-Y. Qi and Y.-Q. Jin, “Analysis of the effects of Faraday rotation on spaceborne polarimetric SAR observations at P-Band,” IEEE Trans. Geosci. Remote Sens., vol. 45, no. 5, pp. 1115-1122, May 2007.

    [8] J. Chen and S. Quegan, “Improved estimators of Faraday rotation in spaceborne polarimetric SAR data,” IEEE Geosci. Remote Sens. Lett., vol. 7, no. 4, pp. 846-850, Oct. 2010.

    [9] C. Senior et al., “E and F region study of the evening sector auroral oval: A Chatanika/Dynamics Explorer 2/NOAA 6 comparison,” J. Geophys. Res.”Space Phys., vol. 92, no. A3, pp. 2477-2494, Mar. 1987.

    [10] J. S. Kim, K. P. Papathanassiou, S. Quegan, and N. Rogers, “Estimation and correction of scintillation effects on spaceborne P-band SAR images,” in Proc. IEEE Int. Geosci. Remote Sens. Symp., Munich, Germany, pp. 5101-5104, Jul. 22-27, 2012.

  • Metrics
    No metrics available
Share - Bookmark