-------------------------------------------------------------------------------
   Computes the link attenuation due to gas. 
   Assumes the signal passes through a fixed slice of atmosphere so that the 
   path
-------------------------------------------------------------------------------
   Form:
   a = LossAtmosphericGas( f, E )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   f              (1,m)  Frequency (GHz)
   E              (1,n)  Elevation angle (deg)

   -------
   Outputs
   -------
   a              (n,m)  Link attenuation

-------------------------------------------------------------------------------
	 Reference: Maral, G. and M. Bousquet. (1998.) Satellite Communications
               Systems, Third Edition. John Wiley. p. 57.
-------------------------------------------------------------------------------