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   Brightness temperature of the sky.
   Will perform a demo. Produces a plot when called without outputs.
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   Form:
   t = TSky( f, e )
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   ------
   Inputs
   ------
   f            (1,n)  Frequency (GHz)
   e            (1,m)  Elevation angle (deg)
                        
   -------
   Outputs
   -------
   t            (n,m)  Temperature
                        
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	References:	Maral, G. and M. Bousquet. (1998.) Satellite Communications
               Systems. Wiley. pp. 36.
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