Explorer 1:
Overview
Explorer 1 was the first spacecraft successfully launched by the U.S. It orbited
Earth every 115 minutes, 358
kilometers (220 miles) above the surface at its closest point and 2550 kilometers (1580
miles) at its farthest. It carried instruments to measure cosmic rays, micrometeorites, and
its own temperature, transmitting this data until February 28, 1958. Explorer 1 found a
radiation belt around Earth, which came to be called the Van Allen radiation belt after the
scientist who built the cosmic ray detector.
Visit the Explorer 1 Website
