2-13] AEW TARGET RESOLUTION REQUIREMENTS 75 



The configuration developed in this manner is one of many that could 

 be developed as a possible problem solution. An actual study would exam- 

 ine a number of such configurations. This example is chosen to illustrate 

 some of the quantitative and qualitative aspects of the system problems 

 that must be considered in an AEW design. 



The specification of detection ranges must take account of the un- 

 certainty attending the detection process. For identical tactical situations, 

 detection by radar will take place within a band of possible ranges, such as 

 are shown by the distribution density function in Fig. 2-19. The proba- 



Probability that Target is Detected 

 before Range Closes to R 

 (Cumulative Probability)- 



f 1.0 



§0.5 



Q. 



Probability that Target 



is Detected between 



Rand R+c/R 



RANGE, R -W-dR 



Fig. 2-19 Characteristic Forms of Radar Detection Probability Distributions and 

 Cumulative Detection Probability Curves. 



bility that the target will be at some time detected bejore it closes to a given 

 range R — customarily called the cumulative probability of detection — 

 is the integral of the distribution density function taken from i? to °o ; its 

 usual form is also shown in Fig. 2-19. 



A preliminary requirements study such as we are performing generally 

 expresses the radar detection requirement in terms of the range for 90 

 per cent cumulative probability of detection. Accordingly, the detection 

 requirements for the AEW radars may be defined as: 



Search Sector — 360° azimuth — Sea level to 50,000 ft. 



Detection Range — 90 per cent cumulative probability of detection of 



the specified enemy targets at 150 n.mi. 



2-13 AEW TARGET RESOLUTION REQUIREMENTS 



A primary function of the AEW system is to provide an early description 

 of potential targets. The description might include range, bearing, eleva- 

 tion, and number of targets. This information is employed in the threat 

 evaluation phase and, later, to vector interceptors against specific targets. 

 In both phases, the ability of the AEW system to resolve separate target 

 elements is of fundamental importance. 



