98 THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 



Total System Position Error (Paragraph 2-15, Equation 2-8) 



At 75 n.mi. 



or = 2 n.mi. rms (5° beam). 

 At 150 n.mi. 



(It = 4.2 n.mi. 



Height-Finding Radar (Paragraph 2-19) 



Threat Evaluation Range 125-150 n.mi. 



Nominal Vectoring Range IS n.mi. 



Azimuth Coverage ± 80° from aircraft nose 



Elevation Coverage 45° up, 18.3° down 



Beamwidth — Elevation 3.2° 



Height Finding Error 0.5 n.mi. rms or 3000 ft rms 



Beamwidth — Azimuth Approx. 5°, to match fan beamwidth 



Stabilization Data stabilized to within 0.27° rms of true 



vertical 



2-21 EVALUATION OF TENTATIVE DESIGN PARAMETERS 

 WITH RESPECT TO THE TACTICAL PROBLEM 



We have discussed the general problems of AEW radar design; we also 

 have hypothesized an AEW System which provides answers to certain of 

 these problems (detection range, resolution, target counting, etc.). Now 

 we shall hypothesize reasonable means for processing the radar information 

 to provide headirig and velocity information in the tactical environment 

 of the example. The accuracy of the heading and velocity estimates 

 obtained — coupled with the position accuracy — form inputs for the study 

 of the interceptor system effectiveness. 



Three minutes (180 seconds) are available to evaluate the threat fol- 

 lowing detection. From Equations 2-13 and 2-14 we see that the standard 

 deviations of the heading and velocity measurements obtained by using 

 the position measurements made at the beginning and end of the 3-minute 

 interval are 



ayr = ^;^"-""- = 0.0233 n.mi./sec = 142 fps rms (2-27) 



180 sec 



(4.2) (6080) (57.3) „ ^^^ ,. oox 



""'' = (800)(180) = ^^-^ ''''' ^^-^^^ 



where 6080 = conversion factor between knots and fps 



57.3 = conversion factor between radians and degrees. 



This accuracy is sufficient to provide a basis for evaluating the threat 

 within the 3-minute period. Actually, the accuracy is somewhat better than 

 is indicated by these figures. As already mentioned, the range resolution 

 capability of the radar allows fifteen of the twenty targets to be resolved at 



