Today in History – January 31, 1958 – Explorer 1 became the United States of America’s first satellite to orbit the Earth after it was launched on January 31, 1958. After the Soviet Union’s successful launch of Sputnik I on October 4, 1957, the United States of America embarked upon a program to launch it own artificial satellite. The first American attempt to launch a satellite using a Vanguard 1 rocket occurred in December 1957 and failed miserably.

Following this failure, the U.S. Army Ballistic Missile Agency, located at Redstone Arsenal in Huntsville, AL, was directed to launch a scientific satellite using a Jupiter C rocket developed under Dr. Wernher von Braun. The artificial satellite was designed, built and operated by the California Institute of Technology’s Jet Propulsion Laboratory under the direction of Dr. William Pickering.

The satellite instrumentation of Explorer 1 was a cosmic ray counter designed by Dr. James Van Allen, a physicist at the University of Iowa. The cosmic ray counter experiment was designed to measure the radiation that surrounds the Earth. Once in orbit, the cosmic ray counter began to overload and measured a much lower cosmic ray count than previously assumed. Given this new information, Dr. Van Allen theorized that the cosmic ray equipment may have been exposed to very strong radiation caused by a belt of charged particles trapped in space by Earth’s magnetic field.

The data returned by Explorer 1 and another satellite launched in March 1958 prove the existence of intense belts of radiation that surround the Earth. These belts of radiation are now called Van Allen Belts and are considered to be the first major scientific discovery of the space age.

Check out the Engineering Pathway’s educational resources on the Explorer I and satellites. For more educational resources, see our aeronautical engineering education and electrical engineering education community pages. The Engineering Pathway also hosts Engineering Education communities in all ABET-accredited disciplines.