Explorer 1 was the first satellite launched by the United States on January 31, 1958. It was part of the International Geophysical Year and marked a significant achievement in the Space Race between the U.S. and the Soviet Union. The satellite was designed to study cosmic rays and gather data about the Earth's atmosphere and radiation. The launch of Explorer 1 was a pivotal moment in space exploration, as it helped discover the Van Allen radiation belts, zones of charged particles trapped by Earth's magnetic field. This discovery advanced our understanding of space and paved the way for future missions and satellite technology.