Accession Number : ADA589142


Title :   SAR Imaging through the Earth's Ionosphere


Descriptive Note : Final rept. 15 Apr 2010-30 Sep 2013


Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH


Personal Author(s) : Tsynkov, Semyon V


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a589142.pdf


Report Date : 06 Nov 2013


Pagination or Media Count : 148


Abstract : Spaceborne imaging of the Earth's surface by synthetic aperture radars (SAR) may be adversely affected by the ionosphere. Image distortions are due to mismatches between the actual radar signals that are subject to temporal dispersion and Faraday rotation in the ionospheric plasma, and their ungarbled form assumed by the SAR signal processing algorithm known as the matched filter. To mitigate the distortions, we propose to probe the terrain and hence the ionosphere on two distinct carrier frequencies. Subsequently, we analyze the resulting two images and accurately evaluate their relative displacement by applying an area-based image registration algorithm. This, in turn, translates into an accurate estimate of the total electron content and its along-the-track gradient in the ionosphere. The latter are the parameters of the plasma that are responsible for the dispersion-induced mismatches between the signal and the filter. In addition to that, image autocorrelation analysis allows us to evaluate the parameters that control the Faraday rotation. Knowing all those parameters, we can correct the matched filter and thus improve the quality of the image. We also analyze the linearized scattering off the target for both isotropic and anisotropic case.


Descriptors :   *IONOSPHERE , *RADAR IMAGES , *SYNTHETIC APERTURE RADAR , AMBIGUITY , ANISOTROPY , BORN APPROXIMATIONS , FUNCTIONS(MATHEMATICS) , MAGNETIC FIELDS , POLARIZATION , PROPAGATION , THEOREMS


Subject Categories : Atmospheric Physics
      Active & Passive Radar Detection & Equipment


Distribution Statement : APPROVED FOR PUBLIC RELEASE