THEORY 



339 



2,5 



CO 



or 



I^^ iO-y°° N(h) dh (m 



I^= 1.4588 + 0.0029611 Ng (m) 

 r = 0.982 

 S.E.= 0.0368nn 



I I I 



250 



350 



Figure 8.17. Integrated refractive index -profiles for the CRPL Standard Sample. 



elevation dependence of integrated N{h) profiles when taken from a 

 sample containing stations at widely differing elevations, such as the 

 Standard Sample. 



It is thus apparent that radio range errors, at least at the higher eleva- 

 tion angles, are primarily a linear function of N s- That this is also true 

 at comparatively low angles is shown in figure 8.18, for ^o = 50 mrad 

 (about 3°) for the same profile sample. The reader should especially note 

 the similarity of the distributions of the points about the regression lines 

 between figures 8.17 and 8.18, showing that the range errors at about 3° 

 are still primarily a function of the integral of A'^ with respect to height, 

 or the range error at 90°. 



It has thus been demonstrated that, theoretically, it should be possible 

 to estimate both the angle of refraction of radio rays and errors in radio 

 range measurements from measurement of the refractive index at the 

 surface of the earth. This should be true for targets in or beyond the 

 atmosphere, at elevation angles down to, and possibly lower than, 3°. 

 In addition, if the behavior of refractive index profiles is similar in differ- 

 ent parts of the world, it should be possible to specify "universal" values 



