The interest in the use of spaceborne synthetic aperture radar (SAR) for collecting earth bio/geophysical information and detecting foliage-obscured targets has been increased. However, the signals are inevitably affected by the ionosphere, particularly at very high frequency and ultrahigh frequency. Thus, it is crucial to understand the potential effects of the ionosphere on SAR systems.First, for analyzing range resolution, in addition to linear and quadratic phase errors due to the background ionosphere, the cubic phase error has to be considered. Second, for analyzing azimuthal resolution, the effects of ionospheric irregularities must be evaluated under the conditions of oblique incidence and anisotropic irregularities. Finally, based on the theory of moment equation, range resolution degradation caused by the multiple scattering have to be studied in the case of anisotropic irregularities.

best regards

there is already developed model for the effect of Foliage on SAR image and my question is there any paper or study has tried to mitigate the effect of foliage on the final image of SAR

Dead colleague Ghazal,

Recently, I have started to follow SAR imaging area in the context of unsupervised filtering base on information theory principles. Depending on the model you have selected to mitigate foliage effects, I think it can be useful to follow some papers addressing the atmospheric effects and in particular high water vapor effects on SAR imaging efficiency.  

 Go through this link, you may get ideas.

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=328106&newsearch=true&searchWithin=%22First%20Name%22:L&searchWithin=%22Last%20Name%22:Novak

Hope it would be helpful.