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Explorer program

The Explorer program was the United States' first successful attempt to launch unmanned space missions. It began as an attempt to place an artificial satellite into orbit during the International Geophysical Year, and became an attempt to catch up with the Soviet Union after that nation's launch of Sputnik I on October 4, 1957.

Over the years, NASA has launched a series of "Explorer" spacecraft carrying a wide variety of scientific investigations. The list below identifies the 74 successful and 4 unsuccessful missions as of this writing (March 2000). As of this writing, Explorers 50 (IMP 8), 67-74 and 77-78 (EUVE, SAMPEX, RXTE, FAST, ACE, SNOE, TRACE, SWAS, FUSE, and IMAGE) are still operating.

NASA's Explorer spacecraft series is not simply the longest running series of spacecraft, it has produced highly-durable (i.e., well-engineered) spacecraft as well. Of the 74 successful Explorer missions depicted, fully five of them had had missions which 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 of 2000, of the ten operational Explorer missions, SNOE and TRACE have operated for about two year, 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. The latest two additions are FUSE (June 1999) and IMAGE (March 2000).


"Explorer program" may also refer to the file browser[?] of Windows, called Windows Explorer[?].

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