dipper@utastro.UUCP (Debbie Byrd) (01/04/85)
The first artificial satellite re-entered the atmosphere on this date in 1958. More on Sputnik 1 -- after this. January 4 The Fate of Sputnik 1 In the fall of the year 1957, the Soviet Union stunned the world with the successful launch of the first satellite, Sputnik 1. That first artificial moon served no purpose other than to broadcast radio evidence of its own movement in orbit. But that was enough -- and Sputnik 1 plunged the world into the space age. The first Sputnik was launched on October 4, 1957. But today's date is important, too -- because this is the date in 1958 that Sputnik re-entered Earth's atmosphere. After more than a thousand orbits, the satellite could no longer resist the drag of the atmosphere. It got closer and closer to Earth with each orbit -- until finally it lost the war against gravity and spiraled downward -- disintegrating as it fell. The ashes of Sputnik 1 -- left when the spacecraft vaporized during re-entry -- were strewn across a large portion of the globe. Since then many artificial moons have been launched -- and many have plunged back toward Earth. Like Sputnik 1, they fall back toward Earth because they lose energy to the drag of the atmosphere. Some satellites orbit very high up. For example, geosynchronous orbit -- which places satellites continually over one spot on the globe -- is 22,000 miles above the surface. That's a safe altitude -- since there is no air that high. But many satellites orbit much lower -- say 200 to 300 miles up -- where there are still millions of air molecules in each cubic inch of space. Friction with this thin air can drain a satellite of its energy of motion -- and eventually cause it to plunge downward. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin