Sputnik 1

Sputnik 1 was launched on October 4, 1957 at the Baikonur Cosodrome. It was the first artificial satellite to be put in orbit around the earth. Its primary mission was to study earth's upper atmosphere. Sputnik 1 was able to successfully calculate the atmospheric density by measuring changes in its orbit over time. Sputnik 1 also provided radio transmission data for the upper atmosphere.

After launch, Sputnik 1 orbited the earth at 29,000 kph / 18,000 mph. Its eliptical orbit brought it to 223 km / 139 miles at its closest point and about 1450 km / 900 miles at its furthest. One orbit took about 96 minutes to complete.

Sputnik 1 transmitted a simple "Beep - Beep - Beep" back to earth at frequencies 20.005 MHz and 40.002 MHz. Any amateur radio operator could hear the signals with a proper radio.

Below are three authentic recordings of Sputnik 1 transmissions:

Washington DC Recording

German Recording

Czechoslovakian Recoding

Sputnik 1 broadcast this signal until its batteries died 22 days later on October 26, 1957.

Although some of the launch debris could be seen from Earth, Sputnik 1 was barely visable to the naked eye. It was merely 58 cm / 23 in in diameter and appeared as a 6th magnitude star, which is on the extrememe end of what the human eye can see.

After three months of orbiting the earth, and 60 million km / 37 million miles later, Sputnik 1 reentered earth's atmosphere on January 4, 1957.