At a mere 31 pounds, it was tiny by today’s spacecraft
standards. Yet, as it sprang skyward from Cape Canaveral,
Fla., 45 years ago today, Jan. 31, 1958, aboard a Jupiter-C
rocket, the Explorer 1 satellite carried with it the enormous
hopes and dreams of Cold War America. The country was still
reeling from the Soviet Union’s shocking launches of Sputnik
1 and 2, and the failure of America’s first Vanguard launch
in the month before.

The rocket was quickly swallowed by the night sky. For 90
long minutes President Eisenhower and America waited tensely
to learn the fate of the mission. Finally, from a California
desert tracking station came the message, “Goldstone has the
bird.” America had launched its first Earth-orbiting
satellite and entered the Space Age.

Today we remember Explorer 1 for both its pioneering place in
U.S. space history and its immediate contributions to
science, as the discoverer of the Van Allen Radiation Belts.
For Explorer’s developers, the people of NASA’s Jet
Propulsion Laboratory (JPL), Pasadena, Calif., operated then
by the U.S. Army, those memories are fond indeed. JPL is
managed for NASA by the California Institute of Technology in
Pasadena, Calif.

Dr. William Pickering, then JPL’s director and leader of the
project, recalls the media’s reaction to Explorer 1’s
success. “We were told there was going to be a press
conference at the National Academy of Sciences (in
Washington). About 2 a.m. we got into a car and drove over to
the Academy. I can remember sitting in that car with (Dr.
James) Van Allen and (Dr. Wernher) von Braun; just the three
of us. I think all three of us wondered a little bit about
what was going to happen and who was going to be there at
that hour of the morning. They took us around to the back
door of the Academy and into the great hall. It was
completely filled with people. The media were there and very
enthusiastic when we got there. At the end of (the press
conference), I think all three of us realized that life was
going to be different, ” he said.

Explorer 1’s official chronology started in 1954, when the
Army authorized work on a joint Army-JPL program called
Orbiter. In 1955, the government announced plans to launch a
scientific satellite during the International Geophysical
Year (July 1957 to December 1958). Orbiter competed with the
Navy’s Vanguard program, which won, partly because it relied
less on military technology. Despite the decision, JPL
continued developing some Orbiter technology for use in tests
of reentry heat shields for missiles. After Sputnik shocked
the world, Orbiter was renamed Explorer and approved for
development as a backup program. With Vanguard’s failure,
Explorer 1 suddenly found itself front and center.

In just 84 days, Pickering and his JPL team, working with the
U.S. Army Ballistic Missile Agency in Huntsville, Ala., top
military experts, U.S. academia, and legendary rocket science
luminaries, like Dr. Wernher von Braun, developed Explorer
1’s science package and communications system, as well as the
high-speed upper stages for the Jupiter-C rocket. The work
changed JPL’s emphasis from rockets to what sits on top of
them.

Pickering describes the mood around JPL during Explorer 1’s
development as confident. “We regarded ourselves as the
experts in the rocket business, having made both the Corporal
and Sergeant rockets for the Army and having developed most
of the underlying design features of the modern rocket, both
liquids and solids,” he said. “We were confident.”

Explorer 1’s main science experiment was a cosmic ray
detector built by Dr. James Van Allen of the State University
of Iowa. It was designed to measure the cosmic radiation,
high-speed ions (atoms stripped of electrons) from the
distant universe, in Earth’s orbit. It sought to measure the
flow of cosmic ray ions of the lowest energies, which are
completely absorbed by the atmosphere and can’t be studied
from the ground.

Explorer 1 was launched into a highly elliptical orbit and
carried no onboard tape recorder. Its data could only be
collected when it was within range of a tracking station. The
data collection soon revealed a mystery: at the low points of
the orbit the cosmic ray count was near the expected value,
but at the high portions of the orbit none were counted at
all. Van Allen theorized the instrument might have been
saturated by very strong radiation from a belt of charged
particles trapped in space by Earth’s magnetic field. Two
months later, Explorer 3 confirmed the existence of these
radiation belts, which became known as the Van Allen Belts.
Explorer 1 made its final transmission on May 23, 1958. It
entered Earth’s atmosphere and burned up on March 31, 1970,
after more than 58,000 orbits.

For more Explorer information on the Internet see:

http://www.redstone.army.mil/history/explorer/explorer.html

For more information about NASA programs via links on the
Internet see: www.nasa.gov