114 THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 



required lock-on range need be known to specify a maximum gimbal angle 

 satisfying search, acquisition, and lock-on requirements. 



The sensitivity of viewing probability to gimbal angle may be obtained 

 by examining similar curves for viewing probabilities of 90, 80, and 70 per 

 cent (Figs. 2-35 to 2-37). For example, a 67° maximum look-angle is 

 required to achieve 95 per cent viewing probability at 10 n.mi. range and 

 75° off the target's nose (Fig. 2-34). For a 90 per cent probability under 

 the same conditions, a 60° maximum look-angle is required (Fig. 2-35). 

 This heavy price suggests that a different allocation of viewing and conver- 

 sion probabilities might yield a result nearer the optimum. 



The required elevation angular coverage is determined by the elevation 

 uncertainty of the vectoring system. As already derived (Paragraph 2-19), 

 the elevation measurement error has a standard deviation of 0.5 n.mi. 

 Thus the probability is virtually unity that the target height is within three 

 standard deviations (1.5 n.mi.) of the vectoring radar system measurement. 

 At a range of 10 n.mi. an AI radar elevation coverage of 17° (0.3 radian) 

 is required to encompass this uncertainty. This requirement varies 

 inversely with the required lock-on range and may be expressed 



6(7//(57.3) , 

 R'l — " ^^^^ 



Search pattern elevation coverage 



(2-49) 



The maximum range dimension Ri of the search volume is the range at 

 which search begins. Its value depends on the required lock-on range and 



100 



§1 80 

 Q Q 



LU UJ 



<=y^ 60 



UJ O 



en rn 



40 



20 



30 60 90 120 150 



ANGLE OFF TARGET'S NOSE, B (deg) 



180 



Fig. 2-35 M 



aximum 



Look Angles Required for 90 Per Cent Probability of Seeing 

 Assigned Target with Collision Vectoring. 



