COMPUTATIONS OF ATMOSPHERIC REFRACTION 377 



Similarly for N s = 377.2 in the exponential tables, 



To, 10. 870 (10 mrad) ~ 13.120 Hirad. 



Again using linear interpolation, but now between the N s = 377.2 and 

 A^, = 344.5 atm, the desired value of r at 3.270 km for A^, = 360.0 and 

 ^0 = 10 mrad is obtained. 



Thus 



400 — 377 2 



T0.10.870(10 n.rad) = 13.120 + (15.159 - 13.120) 404 Q _ 377 2 



= 14.798 mrad. 



For the ^o = 0, 52.4, and 261.8 mrad cases, by similar calculations, using 

 linear interpolation : 



7"o,io.87o, (0 mrad) = 21.386 mrad. 



To, 10. 870, (52.4 mrad) = 5.816 mrad, 

 To, 10. 870, (261.8 mrad) = 1.270 mrad. 



The initial gradient correction method (c) may be used if one deter- 

 mines the A^s* which corresponds to the observed initial gradient and then 

 applies (3.45). The initial A'' gradient is —102.9 N units/km, which, as 

 can be seen from table 3.17, corresponds to the N s = 450.0 exponential 

 atmosphere. Therefore, using the exponential tables of Bean and 

 Thayer [1]^ and (3.45) to determine the bending for the ^o = mrad case, 

 one finds by linear interpolation 



Tio, 000(0) = Tio,ooo (400.0, mrad) + [rioo (450.0, mrad) 

 - Tioo (400.0, mrad)] 

 = 21.309 mrad + [5.908 - 3.657] mrad = 23.560 mrad. 



The Tioo (400.0, mrad) is determined by linear interpolation between the 

 404.9 and 377.2 atm. At h = 20.0 km as given in the tables, 



T2o,ooo (0 mrad) = T2o,ooo (400.0, mrad) + [tioo (450.0, mrad) 

 - r,oo (400.0, mrad)] 

 = 22.191 + [5.908 - 3.657] mrad 

 = 24.442 mrad. 



^Figures in brackets indicate the literature references on p. 423. 



