3-4] 



EFFECT OF SCANNING ON DETECTION PROBABILITY 

 20.4 



i?9o% = 0.87 X 



1.3 



13.7 n.mi. 



159 



(3-44) 



The complete curve of cumulative probability of detection versus range is 

 given in Fig. 3-5 along comparable single-scan curves for both a constant 

 and fluctuating target. 



Finding an Optimum Scan Time. In order to demonstrate how 

 an optimum scan time would be determined, the calculations made above 

 for a scan time of 3 seconds will be repeated for scan times of 1, 2, 5, and 10 

 seconds as well. The values of A^, K, K^'^, Ap, p^^% and R^(^% are given in 

 Table 3-1. 



The detection ranges given in Table 3-1 are plotted in Fig. 3-10. From 

 this figure and the table, it is apparent that the optimum scan time in this 



1 2 3 456789 10 



SCAN TIME (sec) 



Fig. 3-10 Example of Detection Range vs. Scan Time. 



case is the original choice of 3 seconds. Another observation which can be 

 made in Fig. 3-10 is that the optimum is very broad, and it actually does not 

 make a great deal of difference whether a scan time of 2 seconds or 5 seconds 

 is selected if the rest of the system is made compatible. This kind of 



