Astronomy: Explorer-I

On 31 January 1958 the Explorer-I was launched into orbit by the Americans. The rocket was a modified design of the Jupiter-C rocket (a descendent of the V2 rocket), which was designed, built and launched only 84 days after the launch of Sputnik. The rocket was designed and built by the Jet Propulsion Laboratory of the California Institute of Technology under the direction of Dr. William H. Pickering. The satellite instrumentation of Explorer-I was designed and built by Dr. James Van Allen of the State University of Iowa. The thirty pound satellite carried instruments to measure temperatures, and micrometeorite impacts, along with an experiment designed by Dr. Van Allen to measure the density of electrons and ions in space. The measurements made by Van Allen's experiment led to an unexpected and startling discovery: an earth-encircling belt of high energy electrons and ions trapped in the magnetosphere now known as the Van Allen Radiation Belt. Explorer-I, officially known as Satellite 1958 Alpha, ceased transmitting on 28 February 1958, but remained in orbit until March of 1970. Related subject >> Sputnik in 1957

The Explorer-I