Table 10 



MICROWAVE WINDOWS IN THE ATMOSPHERE 



in Figure 8. It can be seen in Figure 8 that the 80- to 100-GHz window 

 is subject to excessive attenuation from rain and fog. If a near all- 

 weather capability is to be achieved, then the 30- to 45-GHz atmospheric 

 window is the highest operating frequency that can be used. 



The spatial resolution and sensitivity of a micro- 

 wave radiometer increase with decreasing antenna beamwidth. A narrow 

 beamwidth can only be obtained by use of an antenna of large size rel- 

 ative to the wavelength. Since antenna aperture size is limited on an 

 airborne platform, it is essential to maximize frequency. Thus, to 

 maximize resolution and sensitivity consistent with the need for all- 

 weather capability, we adopt a frequency of 35 GHz for use in these per- 

 formance estimates. 



(2) Details of the Baseline System 



To make specific performance predictions and cost 

 estimates, a baseline system is postulated with the characteristics 

 summarized in Table 11. 



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