National Geographic : 1956 Apr
© National Geographic Society 496 Satellite Appears to Roam the Globe, Any object in the grip of the air follows earth's rota tion-approximately 1,000 miles an hour at the Equa tor. But a man-made satellite beyond the atmosphere, like the moon itself, will remain independent of earth's spin. A satellite cruising at its ideal speed, 4.737 miles a second at 300 miles altitude, would circle the globe in about 90 minutes. Meanwhile the earth, rotating to the east, would quickly put successive areas into view ing distance of the new heavenly body. Which Actually Rotates Beneath It These five globes show how a satellite's orbit will remain undeviating though the spinning world changes its face from the Americas to Africa. First globe visualizes the satellite having risen into its orbit from Florida. Second figure shows a one-sixth spin by the world as against three revolutions by the satellite. By the time the earth rotates into phase 5 (right), the satellite will have completed 12 revolutions. While the moon comes into view but once a day, the satellite rises and sets 15 times in 24 hours. + First Satellite, Repeatedly Crossing the Equator, Spans a 5,000-mile Belt This Mercator projection, which flattens the world against a sheet of paper, illustrates the announced course of the first IGY satellite-from 40 degrees north of the Equator to 40 degrees south. New York and San Francisco may catch glimpses; Chicago lies too far north. Africa and South America will have grandstand seats; only a part of the U.S .S.R. will be included. Measured at the Equator, earth moves 1,600 miles during one satellite revolution. + Others May Follow the Equator or Cross the Poles Globe No. 1 shows an equatorial launching, which takes fullest advantage of the 1,000-mile-an-hour spin at earth's middle. But this view will satisfy only the relatively few living in the cloudy mid-tropics. Second and third orbits span 60 and 120 degrees of latitude, respectively. Pole-to-Pole satellite (No. 4) sacrifices the launching advantage but covers the world. Near the magnetic poles it gathers data on auroras and cosmic-ray intensities.