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Aviation History
1961
1961 - 0577.PDF
Fl 7HT,4 May 1961 587 H ssiles and Space flight. . . SPACE SCIENCE IN p; i 2: Results from Rockets, Satellites and Tracking HTiHE national reports presented on the first day of the COSPAR1 meeting and space science symposium at Florence, reported X in last week's issue, were followed by four days in whichscientific papers were presented by individual specialists. Sessions were devoted to radio and optical tracking, magnetic observationsby rockets and satellites, telemetry and data recovery, "special events," recent results from instrumented satellites and spacecraft,international reference atmosphere, and scientific research by means of small sounding rockets. This axticle discusses a numberof the major developments reported at the symposium. The tracking of satellites, optically or by radio, is obviously anactivity which is not confined to the two major satellite-launching nations, and the tracking papers at Florence came from manycountries. In her introduction to the session on optical tracking, Prof Alia G. Masevich, of the Astronomical Council of the SovietAcademy of Sciences, noted that the world's optical-tracking teams The United States con- gratulates the Soviet Union. Outside the Palazzo Pitti on April 12, Dr Richard Porter (left), leader of the US delega- tion to the COSPAR sym- posium, shakes hands with Prof Blagonravov, chief Soviet delegate, after hearing news of the first manned orbital flight "Flight" photograph included 96 in Russia, 110 in the United States, 80 in Japan, 24in China, 18 in Holland, nine in Poland, seven in East Germany and five in Czechoslovakia. Although many interesting scientificstudies had been made based on tracking data, much of the infor- mation obtained during the three-and-a-half years of trackingactivity since the launch of Sputnik 1 had not yet been analysed and properly used. The accuracy of visual observations, Mrs Masevich pointed out,was generally limited by accuracy in timing. The best obtainable was a timing accuracy of 0.1 sec, and in general the accuracy ofvisual tracking data did not exceed 0.2-0.3sec, which corresponded to 0.2-0.3° in position. This accuracy could be improved by usingtelescopes which followed automatically the satellite's motion, by taking into account the personal error of the observer, and—mosteffectively—by combining visual observations with photographic documentation. The time had come to discuss seriously the problem of the mosteffective distribution of tracking stations over the globe. Prof Masevich suggested. In particular, there were insufficient stationsin the southern hemisphere. Another suggestion was that the existing net of optical tracking stations should be used for thefurther study of related astronomical problems requiring statistical data, such as observations of meteor showers, occultations of starsby the Moon and planets, and "seeing conditions." In photographic observations, as with optical observations,the timing accuracy lagged behind the accuracy of position deter- mination. The highest photographic accuracy, the Russian professorstated, was achieved at present with the American Baker-Nunn cameras, and in many countries existing astronomical telescopes This diagram, showing the units involved in the Echo I "Tracking Echo I at FLORENCE By Kenneth Owen This Soviet rocket appeared in a launch sequence in a film shown at the COSPAR symposium. The subject of the film was the second "spaceship satellite," launched on August 19, I960, which carried dogs Belka and Strelka, but Prof Anatoly Blagonravov stated in a commentary to the film that this launch vehicle was not the one which had been used on that occasion were used for photographic tracking. The optical tracking of spaceprobes could be carried out only with the help of very large tele- scopes. Examples of the high accuracy of Baker-Nunn cameras haveincluded photographing the six-inch-diameter Vanguard 1 satellite at a distance of 3,000 miles and photographing the 26in Explorer 6satellite at 14,000 miles, and details of these extremely accurate instruments were given in a paper Experience in Precision OpticalTracking of Satellites for Geodesy by George Veis and Fred L. Whipple of the Smithsonian Astrophysical Observatory. TheSmithsonian optical tracking net consists of 12 Baker-Nunn cameras distributed around the Earth between latitudes 32°Sand 36°N. The Baker-Nunn camera, constructed by the SmithsonianObservatory specifically for the precise observation of artificial satellites, is based on a three-axis Super-Schmidt F/l camera witha focal length of 50cm and afield of view of 5° x 30°. It can track along any great circle at a controllable rate, and can photographsatellites of the 12th magnitude. The focal field is spherical, and a 56mm film is used. At a scale of 406"/mm the camera is capable of providing direc-tions with an accuracy of ±2". A time unit controlled by a crystal clock indicates the instant of the middle of the exposure to0.0001 sec. In practice, however, the timing accuracy is considered good at one-tenth of this.The optical system of the camera was designed by James G. Baker and manufactured by the Perkin-Elmer Corp. The mechani-cal design was by Joseph Nunn and the cameras built by the Boiler and Chivens Company. The first camera was put into operation inNew Mexico in November 1957 and the twelfth in Hawaii in June 1958. Ten other cameras were constructed, located in Argen-tina, Australia, Curacao, Florida, India, Iran, Japan, Peru, South Africa and Spain. Each station is equipped with a Baker-Nunn camera, a Norrmancrystal clock and other auxiliary equipment for power regulation, film processing, film reduction and rapid communication. Most ofthe stations are staffed by six men, and the network is supported by a technical and administrative staff in Cambridge, Massachusetts. It is unlikely, the authors suggest, that any satellite orbiting nearEarth would exceed the range of the Baker-Nunn camera. ECHO 1 BALLOON t Propulsion Labora- " Bell Telephone and Mr Walter K. Victor of JPL JET PROPULSION LABS,GOLDSTONE, CALIFORNIA BELL TELEPHONE LABS,HOLMDEL, NEW JERSEY I GODOARD SPACE FLIGHT CENTER COMPUTER
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