SATELLITE-TRACKING PROGRAM — HAYES 317 



lite 1958 Epsilon, it had an apogee of 1,380 miles, a perigee of 163, 

 and a period of 110.27 minutes. Its instrumentation, consisting of 

 geiger and scintillation counters and two transmitters, was designed 

 to telemeter to earth new data on the radiation belts. Its radio signals 

 failed on October 6, and the satellite came down on October 23, 1959. 



The Observatory had proposed to ABMA in May 1958 that it 

 monitor the two Explorers, and furnish space-time coordinates in a 

 special form adapted to the specific purpose of the experiments carried 

 in the satellites to ensure the ultimate value of the telemetered data. 

 This latter work was to be conducted in conjunction with the tracking 

 operations. Dr. Charles A. Lundquist coordmated the program for 

 ABMA; Dr. G. F. Schilling, for the Somthsonian Astrophysical 

 Observatory. 



The first Baker-Numi photographs of Explorer IV were obtained 

 34 hours after launch. Within a few days, the Observatory was able 

 to supply ABIMA with minute-by-minute positions of the satellite. 

 It also prepared orbital elements on a regular basis throughout the 

 lifetime of the radio transmitter. In all, 130 photographic and 250 

 Moonwatch observations of the satellite were obtained. 



In addition, the contract between the Observatory and ABMA 

 provided that various computer programs be written, particularly 

 a numerical integration program and a differential correction proce- 

 dure, both based on work done by Dr. Leland Cunningham. This 

 cooperative undertaking proved to be highly successful. Explorer 

 IV was the first satellite for which ephemerides were reproduced 

 in multiple copies and sent in a brief time — a matter of a few days 

 or a week — to all interested parties. This procedure has now become 

 routine. 



As for the Observatory, the success of the project reflected the re- 

 fined skill of the satellite-tracking network, a skill that was to ensure 

 the continuance of the network after the IGC. 



MOONWATCH 



By early 1958, the Moonwatch network consisted of 230 teams ; 121 

 of them were Avithin the continental United States, 1 in Canada, 

 13 in South and Central America, 77 in Japan, 5 in Australia, 5 in 

 other islands in the Pacific, 3 on the Asia mainland, and 5 in Africa. 

 During the first quarter of the year, the Observatory received 1,371 

 observations from the teams; 1,272 of these were of Satellite 1957 

 Beta, 85 of 1958 Alpha, 8 of 1958 Beta, and 6 of 1958 Gamma. Moon- 

 watch observations since October now totaled 3,141. 



These observations were of unique and vital importance, especially 

 since the radio signals from Sputnik I ceased 3 weeks after its launch- 

 ing on October 4, and those from Sputnik II ceased 7 days after it was 



