Launch date: January
31, 1958 (Feb. 1, 1958 using Universal
Launch vehicle: Jupiter
Time to orbit Earth:
Furthest orbital distance from
2,515 kilometers (1,563 miles)
Closest orbital distance to Earth
(perigee): 354 kilometers (220 miles)
After the Soviets launched the first satellite, Sputnik,
in October 1957, the pressure was on the United States
to build and launch a satellite of its own. Although the
first satellite we tried (the Vanguard,
in December 1957) didn't make it off the launch pad, the
Explorer 1 was designed and successfully launched in just
Explorer 1 team, which included James Van Allen, equipped
the satellite with instruments to measure micrometeorite
impacts, the internal and external temperature of the
satellite, and above all, the concentration of ions and
electrons in space. Van Allen was searching for information
on cosmic rays, which are fast ions coming from space.
But when he found fewer rays than he expected, he guessed
that the satellite's readings must have been thrown off
by areas of high radiation in space, coming from highly
charged particles caught in the Earth's magnetic field.
These areas became known as Van Allen radiation belts
when their existence was confirmed by another satellite
a few months later.
from Explorer 1 were sent back to Earth for about four
months, but the satellite continued to orbit until March
31, 1970, when it burned up after entering the Earth's
Science Center's Explorer 1
Our Explorer 1 is an engineering model of the satellite,
on loan to us from the NASA Jet Propulsion Laboratory,
located in Pasadena.
Missions - Explorer 1-5
This official site from JPL highlights the facts about
the Explorer missions and also includes links to additional
to Explore Earth: Explorer 1
As part of its Solar System Exploration site, JPL includes
this page on the Explorer 1 along with an interesting
collection of links. If you're interested in space exploration,
be sure to click the link to the Solar System Exploration
home page for the latest space news.
Exploration of the Earth's Magnetosphere
Discover all you ever wanted to know about the magnetosphere,
including information on the Van Allen radiation belts,
at this amazingly detailed site, which also includes
a Spanish translation.