Explorer program
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- This article is about the space exploration program. "Explorer program" may also refer to the file browser of Windows, called Windows Explorer.
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 an 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 I on October 4, 1957. (See: Sputnik crisis) Explorer 1 was launched February 1 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 unmanned space 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 J), 67-74 and 77-83 (EUVE, SAMPEX, RXTE, FAST, ACE, SNOE, TRACE, SWAS, FUSE, IMAGE, WMAP, HESSI, 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, fully five of them had had missions which lasted 10 or more years, the longest of which (IMP J) 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.
Mission History
| Explorer | Name | Launch Date | Mission |
|---|---|---|---|
| 1 | Explorer 1 | February 1 1958 | Energy particles studies, discovered the Van Allen radiation belt |
| 2 | Explorer 2 | March 5 1958 | Failed to achive orbit |
| 3 | Explorer 3 | March 26 1958 | Energy particles studies |
| 4 | Explorer 4 | July 26 1958 | Energy particles studies |
| 5 | Explorer 5 | August 24 1958 | Failed to achive orbit |
| -- | S-1 | July 16 1959 | Failed to achive orbit |
| 6 | S-2 | August 7 1959 | Magnetosphere research |
| 7 | S-1a | October 13 1959 | Energy particles studies |
| -- | S-46 | March 23 1960 | Failed to achive orbit |
| 8 | S-56 | November 3 1960 | Measured atmospheric composition of the ionosphere |
| -- | S-56 | December 4 1960 | Failed to achive orbit |
| 9 | S-56a | February 16 1961 | Atmospheric density measurments |
| -- | S-45 | February 24 1961 | Failed to achive orbit |
| 10 | P-14 | March 25 1961 | Investigated field magnetic field between the earth |
| 11 | S-15 | April 27 1961 | Gamma ray astronomy |
| -- | S-45a | May 25 1961 | Failed to achive orbit |
| -- | S-55 | June 30 1961 | Failed to achive orbit |
| 12 | EPE A | August 16 1961 | Energetic particles research |
| 13 | S-55a | August 25 1961 | Micrometeoroids research |
| 14 | EPE B | October 2 1962 | Energetic particles research |
| 15 | EPE C | October 27 1962 | Energetic particles research |
| 16 | S-55b | December 16 1962 | Micrometeoroids research |
| 17 | AE A | April 3 1963 | Atmospheric research |
| 18 | IMP A | November 27 1963 | Magnetospheric research |
| 19 | AD A | December 19 1963 | Atmospheric density measurments |
| 20 | IE A | August 25 1964 | Ionosphere research |
| 21 | IMP B | October 4 1964 | Magnetospheric research |
| 22 | BE B | October 10 1964 | Ionospheric and geodetic research |
| 23 | Explorer 23 | November 6 1964 | Micrometeoric research |
| 24 | AD B | November 21 1964 | Atmospheric density measurments |
| 25 | Injun 4 (IE B) | November 21 1964 | Ionospheric research |
| 26 | EPE D | December 21 1964 | High energy particle observations |
| 27 | IMP C | April 29 1965 | Magnetospheric research |
| 28 | IMP C | May 29 1965 | Magnetospheric research |
| 29 | GEOS A | November 6 1965 | Geodetic earth monitoring |
| 30 | Solrad 8 (SE A) | November 19 1965 | Solar radiation monitoring |
| 31 | DME A | November 29 1965 | Ionospheric research |
| 32 | AE B | May 25 1966 | Atmospheric research |
| 33 | IMP D | July 1 1966 | Magnetospheric research |
| 34 | IMP F | May 24 1967 | Magnetospheric research |
| 35 | IMP E | July 19 1967 | Magnetospheric research |
| 36 | GEOS B | January 11 1968 | Geodetic earth monitoring |
| 37 | Solrad 9 (SE B) | March 5 1968 | Solar radiation monitoring |
| 38 | RAE A | July 4 1968 | Radio astronomy |
| 39 | AD C | August 8 1968 | Atmospheric density measurments |
| 40 | Injun 5 (IE C) | August 8 1968 | Magnetospheric Research |
| 41 | IMP G | June 21 1969 | Magnetospheric research |
| 42 | SAS A | December 12 1970 | X-Ray Astronomy |
| 43 | IMP H | March 13 1971 | Magnetospheric research |
| 44 | Solrad 10 (SE C) | July 8 1971 | Solar radiation monitoring |
| 45 | SSS A | November 15 1971 | Magnetospheric research |
| 46 | MTS A | August 13 1972 | Micrometeoroids research |
| 47 | IMP I | September 23 1972 | Magnetospheric research |
| 48 | SAS B | November 15 1972 | X-Ray Astronomy |
| 49 | RAE B | June 10 1973 | Radio astronomy |
| 50 | IMP J | October 26 1973 | Magnetospheric research |
| 51 | AE C | December 16 1973 | Atmospheric research |
| 52 | Injun 6 (IE D) | June 3 1974 | Magnetospheric research |
| 53 | SAS C | May 7 1975 | X-Ray Astronomy |
| 54 | AE D | October 6 1975 | Atmospheric research |
| 55 | AE E | November 20 1975 | Atmospheric research |
| 56 | ISEE 1 | October 22 1977 | Magnetospheric research |
| 57 | IUE | January 26 1978 | Ultraviolet astronomy |
| 58 | HCMM | April 26 1978 | Thermal mapping of the earth |
| 59 | ISEE 3 (ICE) | August 12 1978 | Magnetospheric research |
| 60 | SAGE | February 18 1979 | Stratospheric aerosol and ozone data |
| 61 | Magsat | October 30 1979 | Mapped the near surface magnetic field of the Earth |
| 62 | DE 1 | August 3 1981 | Magnetospheric research |
| 63 | DE 2 | August 3 1981 | Magnetospheric research |
| 64 | SME | October 6 1981 | Atmospheric research |
| 65 | CCE | August 16 1984 | Magnetospheric research |
| 66 | COBE | November 18 1989 | Microwave astronomy |
| 67 | EXUV | June 7 1992 | Ultraviolet astronomy |
| 68 | SAMPEX | July 3 1992 | Magnetospheric research |
| 69 | XTE | December 30 1995 | X-ray astronomy |
| 70 | FAST | August 21 1996 | Auroral phenomena |
| 71 | ACE | August 25 1997 | Solar/interplanetary/interstellar partical research |
| 72 | SNOE | February 26 1998 | Atmospheric research |
| 73 | TRACE | April 2 1998 | Solar observatory |
| 74 | SWAS | December 6 1998 | Submillimeter astronomy |
| 75 | WIRE | March 5 1999 | InfraRed astronomy, primary mission failed due to loss of coolant |
| 76 | TERRIERS | May 18 1999 | Atmospheric research, satellite failed shortly after achiving orbit |
| 77 | FUSE | June 23 1999 | Ultraviolet astronomy |
| 78 | IMAGE | March 25 2000 | Magnetospheric research |
| 79 | WMAP | June 30 2001 | Microwave astronomy |
| 80 | RHESSI | February 5 2002 | X-ray and gamma ray solar flare imaging |
| 81 | CHIPSat | January 13 2003 | Ultraviolet spectroscopy and astronomy |
| 82 | GALEX | April 28 2003 | Ultraviolet astronomy |
| 83 | SWIFT | November 20 2004 | Gamma ray astronomy |