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= Radar backscatter statistics =

The received power (intensity) of a radar system is proportional to the (normalized) radar backscatter coefficient 
{{{#!latex 
$\sigma^0(f,p,\theta)$
}}} as a function of frequency, polarization and incidence angle. The backscatter coefficient describes how much of the transmitted energy is backscattered from the surface media. 

A (calibrated) ASAR image ''img(y,x)=I'' is made of the measured intensities ''I'' which can be directly related to the backscatter coefficient. A value of zero means that no energy is reflected from the surface whereas a value of one means the total reflection.

= Exercise =
This [[attachment:ASAR_seaice_mixed_20080421_f32_1000x1000|ASAR image]] shows different sea ice types. Investigate the statistic of normalized backscatter value. 

 * What is the mean for the two prevalent sea ice types? Select homogeneous regions to answer this question.
 * Try to fit the image PDF with a superposition of two gamma distributions (ADVANCED EXERCISE).

{{{#!pyton
from pylab import *
sigma0=reshape(fromfile('ASAR_seaice_mixed_20080421_f32_1000x1000.dat',dtype=float32),(1000,1000))
}}}