Explorer program

The Explorer program was the United States's first successful attempt to launch an artificial satellite. It began as a U.S. Army proposal to place a scientific satellite into orbit during the International Geophysical Year. That proposal was rejected in favor of the U.S. Navy's Project Vanguard. It was revived as a crash program to catch up with the Soviet Union after that nation's launch of Sputnik 1 on October 4, 1957. ("See:" Sputnik crisis) Explorer 1 was launched January 31 1958. Besides being the first U.S. satellite, it is known for discovering the Van Allen radiation belt.

Explorer at NASA

The Explorer program was taken over by NASA, which continued to use the name for robotic spacecraft missions.

Over the years, NASA has launched a series of "Explorer" spacecraft carrying a wide variety of scientific investigations. The list below identifies the 79 successful missions as of December 2004. As of this writing, Explorers 50 (IMP-8), 68-71, 73-74, 79-83 (SAMPEX, RXTE, FAST, ACE, TRACE, SWAS, WMAP, RHESSI, CHIPSat, GALEX and SWIFT) are still operating.

NASA's Explorer spacecraft series not only is the longest running series of spacecraft, it has produced highly-durable, well-engineered spacecraft as well. Of the 79 successful Explorer missions depicted, five of them had missions that lasted 10 or more years, the longest of which (IMP-8) has been operational for over 26 years now and still produces valuable information about the solar wind. NASA's IUE spacecraft operated for 19 years and produced copious amounts of data for the astronomical community. The ISEE 3/ICE spacecraft operated for 14 years. As of March 2000, of the ten operational Explorer missions, SNOE and TRACE have operated for about two years, ACE two and a half years, FAST for about three and a half, RXTE for over four, EUVE and SAMPEX for nearly eight, and IMP 8 for more than 26. SWAS has been operational for slightly more than one year, having been launched in early December 1998.

; Energetic Particle ExplorersExplorers 12, 14, 15 and 26 were the S 3 series of spacecraft, known as Energetic Particle Explorers. They were spin-stabilized, solar-cell-powered spacecraft instrumented to measure cosmic ray particles, trapped particles, solar wind protons, and magnetospheric and interplanetary magnetic fields. [cite web
url = http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1961-020A
title = Explorer 12
publisher = NASA]

Mission History

References

See also

* Small Explorer program

External links

* [http://explorers.gsfc.nasa.gov/missions.html NASA Explorer program missions page]
* [http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Explorer_Moon Explorer Program Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://w3.armed.us/explorer 1957 Video (30 minutes) on launch and impact of Explorer]
* [http://www.cira.colostate.edu/cira/RAMM//hillger/acronyms.htm Master list of Names, Initialisms, and Abbreviations for un-manned satellites]