Explorer is the first and most extensive satellite and spacecraft program of the United States.
In 1957, the Soviet Union decided with the Sputnik 1, the race for the first artificial satellite in space for itself. It had officially begun with the announcement of the U.S. President on 28 July 1955 to promote as part of the International Geophysical Year an artificial satellites into orbit. The Soviet Union had a few days later officially declared the same intention.
The U.S. was actually not yet ready to use with their Vanguard project at the time of the Sputnik launch and tried in late 1957 with an early start as a response to this so-called Sputnik shock. However, the launch ended in disaster: The hitherto never been fully tested carrier rocket exploded at the start still on the launch pad before the eyes of millions of television viewers.
The Explorer series, this gave the chance to lift the first satellite into orbit, and was extremely successful over the Vanguard Project. On February 1, 1958 Explorer 1 launched the first American satellite successfully into orbit. Under the name displays more than 82 successful missions have been carried out in various fields of research, from the study of the ionosphere on the radio astronomy to atmospheric and earth observation. These mainly by the Army in Huntsville (Alabama ) developed satellites, with the help of the experienced group led by former technical director Wernher von Braun the former Army Research Center Peenemünde, the first U.S. satellite in orbit were thus - and thus an important first step towards manned space flight.
Each Explorer satellite ( since Explorer 6 ) carries a Subbezeichnung - depending on which scientific project he belonged.
Since the early 1990s, sub-programs was started in the Explorer program:
- SMEX (Small Explorer ) for small research missions since the early 1990s.
- MIDEX (Middle - Sized Explorer) for Medium Research Satellite from the late 1990s.
- Stedi ( Student Explorer Demonstration Initiative) and UNEX ( University Explorer) for small, conducted by universities for NASA missions.
A complete listing of the 102 so far launched Explorer satellites can be found in the list of Explorer missions.