Durable Orange

Nikita Khrushchev laughed when the U.S. finally got Vanguard I into space, and likened it to an orange. Last week the 3 1/4-lb. satellite soared into its second year in regions where huge Russian satellites have long since died. Vanguard's orbit, which climbs up to 2,500 miles and never comes lower than 400 miles, has hardly changed. Vanguard I has traveled something over 132 million miles. Its clear radio voice, powered by solar batteries, is still chirping as cheerily as ever, is expected to hold out for at least 200 years.

Vanguard has proved so regular, and its orbit can be charted so exactly, that it has been used to plot, with an accuracy never before possible, the exact position of oceanic islands. In the past, islands were mapped by celestial observations whose accuracy depended on the establishment of an exact vertical by gravity. Because of uncertainties about the earth's shape, this can be done precisely only at the poles. So the Army Map Service sets up mobile tracking stations on various islands. When Vanguard I passes overhead, the trackers determine its bearing at an exact time, in microseconds. Stations on the mainland, which have been following the satellite for a year, can calculate Vanguard's position in space at the instant when it was observed from the island. From this information the position of the island can be charted. As a result, points on Wake, Guam and Kwajalein have been found to be almost one mile out of position. The islands are being replotted with a maximum possible error of less than 50 ft.

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