Explorer I: Timeline

1958   The first successful American satellite Satellite

A satellite is any object that orbit [i]s another object . ... 

, Explorer I, is launched into orbit.

1958   Explorer I ceased transmission

1970   NASA's NASA

The National Aeronautics and Space Administration is an agency of the United States Government [i], res ... 

 Explorer I, the first American artificial satellite Satellite

A satellite is any object that orbit [i]s another object . ... 

 and the first of the Explorer program Explorer program

The Explorer program was the United States [i]'s first successful attempt to launch an artificial satellite [i] ... 

 spacecrafts, reenters Earth's atmosphere after 12 years in orbit.