DEPENDENCE ON CLASS 



399 



Table 3. Dependence of target strengtli of submarine cla.ss (indirect measurements). 



ASPECT ANGLE IN DEGREES 



Figure 13. Comparison of theoretical, optical, and acoustical target strength of the U570 (HMS/M Graph). 



Each submarine class will often evidence its own 

 peculiar reflecting characteristics at certain aspects 

 and altitudes. A striking example of this is the value 

 of 20.2 db for the target strength of the U570 at an 

 aspect of 120 degrees, reported in the Mountain 

 Lakes measurements. Contrast this value with a 

 maximum target strength of 26.3 db for beam as- 

 pects, 9.4 db astern, and 17.4 db bow-on. This result 

 is attributed to a strong specular echo from the back- 

 plate of the conning tower, but is not confirmed by 



optical tests, perhaps because of differences in the two 

 models. 



To test the reliability of these model results for 

 each class of vessel, a comparison may be made be- 

 tween results obtained by different indirect methods 

 on the same type of submarine. Such a comparison is 

 made in Figure 13, which shows target strength 

 plotted against angle for the U570, as calculated 

 theoretically and measured optically and acous- 

 tically. 



