352 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



field-reduced satellite position and time were sent to Cambridge, the 

 errors in timing became, of course, a source of errors in new predictions 

 generated from them. 



COMPUTATIONS 



The Soviet Union told the outside world little concerning the orbits 

 of Sputniks I and II. In fact, much of the data they distributed to 

 the Western press and to the IGY consisted merely of the times of 

 transit over major cities in both hemispheres. Nevertheless, scientists 

 of the Smithsonian Astrophysical Observatory and those of other 

 agencies and organizations were able in a very short time to issue 

 relatively accurate information and even, later, to predict the demise 

 of Sputnik II so precisely that the Kussians claimed they must be 

 fabricating rather than forecasting. 



The problems that confronted the computations staff on the night 

 of October 4 seemed overwhelming. The orbital programs that had 

 been worked out by Drs. Cunningham and Lautman could not be used 

 in tracking Sputnik I. The initial orbit determination program that 

 Slowey and Briggs had written was still being debugged and would 

 not be ready for a day or two for practical computations. 



None of these programs included air drag; scientists everywhere 

 had believed that it would have only a small effect on the orbit of an 

 artificial earth satellite because they greatly underestimated the at- 

 mospheric density between 100 and 200 km. above the surface of the 

 earth. 



Then too, the United States had planned to launch its first satel- 

 lite — which it assumed would be the first satellite — at a height at 

 which air drag would not have been a very important factor. Sput- 

 nik I, however, was moving low in the atmosphere. 



Furthermore, the errors of the first observations received by the 

 Observatory were much larger than those that astronomers were ac- 

 customed to in the study of celestial mechanics. The computation 

 methods at hand were necessarily sensitive to errors of observations, 

 so that when the observations were poor, the orbit derived from them, 

 if one could be derived at all, was necessarily poor. 



Finally, the practical philosophy of the Smithsonian Astrophysical 

 Observatory was to accumulate as many observations as possible, 

 rather than to work with a minimum number from the field. Ulti- 

 mately, the effort to combine dozens of observations into the determina- 

 tion of an orbit proved highly successful. At first, however, provi- 

 sional tecliniques had to be developed to use whatever data were at 

 hand. 



The Observatory was not, of course, alone in this dilemma. The 

 satellite-orbit programs of other observatories failed initially for 

 much the same reasons. In all fairness, it should be noted that no 



