[Illustration: 4. Model of _Sputnik 1_, the first man-made object to
be placed in Earth-orbit.]
_Sputnik 1_, the first man-made object to be placed in orbit around
Earth, was launched by the USSR on October 4, 1957.
A 29-meter (96-foot) rocket with 510,037 kilograms (1,124,440 pounds) of
thrust boosted _Sputnik 1_ into orbit. The satellite’s orbital and radio
data provided scientists with information on atmospheric and electron
densities. _Sputnik 1_ transmitted temperature data for 22 days before
its batteries ran down.
The 83.5-kilogram (184-pound) satellite reentered the earth’s atmosphere
and burned up on January 4, 1958.
This _Sputnik_ model is from the USSR Academy of Sciences.