Explorer 1:
Goals: 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 2,550 kilometers (1,580 miles) at its farthest. It carried instruments to measure cosmic rays, micrometeorites, and its own temperature, transmitting this data until February 28, 1958.

Accomplishments: Explorer 1 found a radiation belt around Earth, which came to be called the Van Allen radiation belt after James Van Allen, the scientist who built the cosmic ray detector. It also proved the United States could successfully launch a satellite into Earth orbit.

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1 Feb 1958:  Launch (31 Jan. 1958, 10:48 p.m. EST) (03:48 UT) 28 Feb 1958:  Last Data Transmitted Status:  Successful		15 May 2007:  The Re-Entry Test Vehicle Program 9 Aug 2006:  Space Pioneer James van Allen Dies 16 Mar 2004:  Space Pioneer Dies More Headlines
Dr. Wernher von Braun led the Jet Propulsion Laboratory team (right) that completed Explorer 1's design in only 3 months. Explorer 1 completed 58,000 orbits times before returning to Earth in March 1970. The first U.S. attempt to launch an Earth-orbiting satellite - Vanguard -- rose a few feet above the ground but then fell back to Earth and burst into flames.		Solar System Bodies: Earth Explorer 1 Multimedia Gallery NSSDC Master Catalog: Explorer 1 NASA Explorer 1 Homepage Explorer 1 50th Anniversary Multimedia