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Solar System Exploration
Explorer 1
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Explorer 01
Explorer 1 Mission to Earth

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 May 23, 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.

Key Dates
1 Feb 1958:  Launch (31 Jan. 1958, 10:48 p.m. EST) (03:48 UT)
23 May 1958:  Last Data Transmitted
31 Mar 1970:  Re-entered Earth's Atmosphere
Status: Successful
Fast Facts
Explorer 01 Facts Dr. Wernher von Braun led the Jet Propulsion Laboratory team (right) that completed Explorer 1's design in only three 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.
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Last Updated: 21 May 2013