Discovering the Cosmos with Small Spacecraft: The American Explorer Program

Explorer was the original American space program and Explorer 1 its first satellite, launched in 1958. Sixty years later, it is the longest continuously running space program in the world, demonstrating to the world how we can explore the cosmos with small spacecraft. Almost a hundred Explorers have already been launched.

Explorers have made some of the fundamental discoveries of the Space Age. Explorer 1 discovered Earth’s radiation belts. Later Explorers surveyed the Sun, the X-ray and ul...