SATELLITE-TRACKING PROGRAM — HAYES 345 



Table 3. — Atmospheric Densities Derived by Various Investigators 



their origin had to be sought in the atmosphere itself rather than in 

 the shape of the satellite. 



Dr. Jacchia discovered that the oscillations had a period of approxi- 

 mately 27 days, equal to that of the sun's rotation, and immediately 

 surmised that the cause of the variations of density in the atmosphere 

 revealed by these variations of drag might be solar radiation. 



He outlined this possibility in a paper entitled "The Erratic Orbital 

 Acceleration of 1957 Beta" in the April 1958 issue of Sky and Tele- 

 scope. When Dr. Wolfgang Priester of Germany studied the text, 

 he noted that the curve of the drag of Sputnik II resembled the varia- 

 tions of the 20-cm. radio flux from the sun. The resemblance could 

 not be seen clearly because unfortunately there were just two minima 

 and one maximum on the curve, and the satellite's perigee went from 

 night into day and back into night exactly at the time when the drag 

 was rising and then declining. The curves did, however, appear to 

 be similar. 



By the time Priester had made this analysis, Jacchia had many more 

 data at hand, including several months of observations of Vanguard 

 I for which he had not published any detailed accelerations. Since 

 he did not have access to the 20-cm. flux, which is measured in East 

 Berlin, he made use of the 10-cm. flux which behaves very much like 

 the other, and which is measured in Canada. He plotted the 10-cm. 

 flux against the drag of Vanguard I. The two curves were almost 

 identical : every single minimum and maximum in one was reflected in 

 the other. There could no longer be any doubt of a relationship be- 

 tween something that was happening in the sun and something that 

 was happening in the atmosphere to affect the motion of the satellite. 



It must be emphasized that there is no direct causal relationship 

 between the 10-cm. flux and the variations of the density, since the 

 atmosphere is completely transparent to that radiation and therefore 



