Fifty years have passed since the United States answered Soviet Union’s challenge and launched Explorer I into space on January 31, 1958, as part of the International Geophysical Year program, from LC-26 at Cape Canaveral Air Force Station in Florida.

The mission was the result of a time trial race, after the Soviet satellite Sputnik I had already made its space debut on October 4, 1957. The project was completed in 84 days, 6 days earlier than the initial deadline, an impressive effort from the American scientists. The “space race” how it has been called had begun.

The U.S. took the lead after the launch, reaching beyond Sputnik I’s discoveries, that simply orbited the Earth, and identifying the high and low activity regions now known as the Van Allen belts, which further opened the path to learning the origins of the aurora borealis and the propagation of radio waves.

The discovery of the Van Allen belts was an intensely celebrated moment by the media and an outstanding moment for the International Geophysical Year. The three people responsible for the great success of the Explorer I were Dr. William H. Pickering, Dr. James A. van Allen and Dr. Werhner von Braun.

The first American satellite into space weighted 13.97 kg, much lighter than the Soviet one (83.6 kg) and was placed on an orbit with 360 kilometers perigee and 2,520 kilometers apogee. The electrical power was based on mercury chemical batteries, and lasted until May 23, 1958, when the satellite stopped transmitting data.

The journey into space of Explorer I ended 12 years later, when the satellite made an appearance over the Pacific Ocean on March 31, 1970. Similar spacecrafts have been sent into space the same year, including Explorer 3, successfully launched on March 26, 1958, and Explorer 4, launched July 26, 1958.