NASA’s Explorer 1 satellite was launched into orbit by a Jupiter-C rocket in January 1958.
The Jupiter-C was a modified version of the Jupiter missile, developed by the U.S. Army Ballistic Missile Agency. It used clustered solid-fuel motors and an additional upper-stage system to give Explorer 1 enough speed to reach orbit.
Explorer 1 was the first U.S. satellite and carried instruments designed by James Van Allen’s team. Its measurements led to the discovery of the Van Allen radiation belts, making the launch scientifically important as well as politically significant.
The Jupiter-C is sometimes confused with the Redstone rocket used for early crewed Mercury flights. Although both were related to American missile technology, Jupiter-C launched Explorer 1, while Redstone later carried astronauts such as Alan Shepard.