Explorers program

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For other uses, see Explorer (disambiguation).
An explorer mission observes the Milky Way's black hole flaring

The Explorers program is a United States space exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space.[1] Over 90 space missions have been launched since 1958, and it is still active. Starting with Explorer 6, it has been a NASA program, and they have worked with a variety of other institutions and business, including many international partners.

History[edit]

Explorer 1's Jupiter rocket ignites
Sputnik caused an uproar in the West

The Explorers program was the United States's first successful attempt to launch an artificial satellite. It began as a U.S. Army proposal (Project Orbiter) to place a scientific satellite into orbit during the International Geophysical Year; however, that proposal was rejected in favor of the U.S. Navy's Project Vanguard. The Explorers program was later reestablished 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.

The Explorers program was transferred to NASA, which continued to use the name for an ongoing series of relatively small space missions, typically an artificial satellite with a science focus. Over the years, NASA has launched a series of Explorers spacecraft carrying a wide variety of scientific investigations.

Explorers satellites have made important discoveries: Earth's magnetosphere and the shape of its gravity field; the solar wind; properties of micrometeoroids raining down on the Earth; much about ultraviolet, cosmic, and X-rays from the solar system and universe beyond; ionospheric physics; Solar plasma; solar energetic particles; and atmospheric physics. These missions have also investigated air density, radio astronomy, geodesy, and gamma ray astronomy. Various space telescopes have made a variety of discoveries, including the first known Earth Trojan asteroid.

The Explorers Program Office at Goddard Space Flight Center in Greenbelt, Maryland, provides management of the multiple scientific exploration missions in the Explorers space flight program. The missions are characterized by relatively moderate cost, and by small to medium sized missions that are capable of being built, tested and launched in a short time interval compared to the large observatories.[2]

Explorers categories have included MIDEX, SMEX, UNEX, and others.[3] A subprogram called Missions of Opportunity (MO) has funded instruments on non-NASA missions.

Launchers have included Jupiter C (Juno I), Juno II, various Thor rockets such as Thor-Able, Scout, various Delta and Delta II rockets of the Delta rocket family, and Pegasus.

Spacecraft by year[edit]

Explorers name numbers can be found in the NSSDC master catalog, typically assigned to each spacecraft in a mission. However, one source says they were not officially assigned after 1975.[4]

Explorers Missions
# Name(s) Launch Date Mission End of Data Re-Entry
1 Explorer 1 January 31, 1958 Energetic particle studies, discovered the Van Allen radiation belt May 23, 1958 March 31, 1970
2 Explorer 2 March 5, 1958 Failed to achieve orbit
3 Explorer 3 (Gamma 1) March 26, 1958 Energetic particle studies June 27, 1958 June 27, 1958
4 Explorer 4 July 26, 1958 nuclear test studies October 5, 1958 October 23, 1959
5 Explorer 5 August 24, 1958 Failed to achieve orbit
7x Explorer 7x (S 1) July 16, 1959 Measure earth's radiation balance, destroyed by range safety
6 Explorer 6 (S-2 (Able 3)) August 7, 1959 Magnetosphere research October 6, 1959 July 1, 1961
7 Explorer 7 (S 1A) October 13, 1959 Energetic particle studies August 24, 1961 In orbit
S 46 March 23, 1960 Analyze electron and proton radiation energies, failed to achieve orbit
8 Explorer 8 (S 30) November 3, 1960 Measured atmospheric composition of the ionosphere December 27, 1960 March 27, 2012
S 56 December 4, 1960 Atmospheric density measurements, failed to achieve orbit
9 Explorer 9 (S 56A) February 16, 1961 Atmospheric density measurements April 9, 1964 April 9, 1964
S 45 February 24, 1961 Ionosphere research, failed to achieve orbit
10 Explorer 10 (P 14) March 25, 1961 Investigated field magnetic field between the Earth and Moon March 25, 1961 June 1, 1968
11 Explorer 11 (S 15) April 27, 1961 Gamma ray astronomy November 17, 1961 In orbit
S 45A May 25, 1961 Ionosphere research, failed to achieve orbit
S 55 (Meteoroid Satellite-A, Micrometeorite Explorer) June 30, 1961 Micrometeoroid research, failed to achieve orbit
12 EPE-A (S 3, Energetic Particle Explorer-A) August 16, 1961 Energetic particle research December 6, 1961 September 1, 1963
13 S 55A August 25, 1961 Micrometeoroid research August 28, 1961 August 28, 1961
14 EPE-B (Energetic Particle Explorer-B) October 2, 1962 Energetic particle research August 11, 1963 July 1, 1966
15 EPE-C (Energetic Particle Explorer-C) October 27, 1962 Energetic particle research January 30, 1963 January 15, 1978
16 S 55B December 16, 1962 Micrometeoroid research July 22, 1963 In orbit
17 AE-A (Atmosphere Explorer-A) April 3, 1963 Atmospheric research July 10, 1963 November 24, 1966
18 IMP-A (IMP 1, Interplanetary Monitoring Platform-A) November 27, 1963 Magnetospheric research May 10, 1965 December 30, 1965
19 AD-A (Atmospheric Density-A) December 19, 1963 Atmospheric density measurements May 10, 1981 May 10, 1981
20 IE-A (S 48, TOPSI, Ionosphere Explorer-A) August 25, 1964 Ionosphere research December 29, 1965 In orbit
21 IMP-B (IMP 2, Interplanetary Monitoring Platform-B) October 4, 1964 Magnetospheric research October 13, 1965 January 30, 1966
22 BE-B (S 66, Beacon Explorer-B) October 10, 1964 Ionospheric and geodetic research February 1970 In orbit
23 S 55C (Explorer 23) November 6, 1964 Micrometeoric research November 7, 1965 June 29, 1983
24 AD-B (Atmospheric Density-B) November 21, 1964 Atmospheric density measurements October 18, 1968 October 18, 1968
25 Injun 4 (IE-B, Ionosphere Explorer-B) November 21, 1964 Ionospheric research December 1966 In orbit
26 EPE-D (Energetic Particle Explorer-D) December 21, 1964 High energy particle observations December 27, 1967 In orbit
27 BE-C (Beacon Explorer-C) April 29, 1965 Magnetospheric research July 20, 1973 In orbit
28 IMP-C (IMP 3, Interplanetary Monitoring Platform-C) May 29, 1965 Magnetospheric research May 12, 1967 July 4, 1968
29 GEOS 1 (GEOS-A) November 6, 1965 Geodetic earth monitoring June 23, 1978 In orbit
30 SOLRAD 8 (SE-A) November 19, 1965 Solar radiation monitoring
(Cover for covert ELINT mission)
November 5, 1967 In orbit
31 DME A November 29, 1965 Ionospheric research October 1, 1969 In orbit
32 AE-B (Atmosphere Explorer-B) May 25, 1966 Atmospheric research March 1967 February 22, 1985
33 IMP-D (AIMP 1, Anchored IMP 1, Interplanetary Monitoring Platform-D) July 1, 1966 Magnetospheric research September 21, 1971[5] In orbit
34 IMP-F (IMP 4, Interplanetary Monitoring Platform-F) May 24, 1967 Magnetospheric research May 3, 1969 May 3, 1969
35 IMP-E (AIMP-E, AIMP 2, Anchored IMP 2, Interplanetary Monitoring Platform-E) July 19, 1967 Magnetospheric research June 24, 1973 In Lunar orbit
36 GEOS 2 (GEOS-B) January 11, 1968 Geodetic earth monitoring July 1, 1982 In orbit
37 Solrad 9 (SE B) March 5, 1968 Solar radiation monitoring
(Cover for covert ELINT mission)
April 30, 1974 November 16, 1990
38 RAE-A (RAE 1, Radio Astronomy Explorer-A) July 4, 1968 Radio astronomy  ? In orbit
39 AD-C (Atmospheric Density-C) August 8, 1968 Atmospheric density measurements June 23, 1971 June 22, 1981
40 Injun 5 (Injun C, IE-C, Ionosphere Explorer-C) August 8, 1968 Magnetospheric Research June 1971 In orbit
41 IMP-G (IMP 5, Interplanetary Monitoring Platform-G) June 21, 1969 Magnetospheric research December 23, 1972 December 23, 1972
42 SAS-A (Small Astronomy Satellite-A, SAS 1) December 12, 1970 X-Ray Astronomy January 4, 1975 April 5, 1979
43 IMP-H (IMP 6, Interplanetary Monitoring Platform-H) March 13, 1971 Magnetospheric research October 2, 1974 October 2, 1974
44 Solrad 10 (SE-C, SOLRAD-C) July 8, 1971 Solar radiation monitoring
(Cover for covert ELINT mission)
June 30, 1973 December 15, 1979
45 SSS-A (S-Cubed A) November 15, 1971 Magnetospheric research September 30, 1974 January 10, 1992
46 Meteoroid Technology Satellite (MTS, METEC)[2] August 13, 1972 Micrometeoroids research November 4, 1974 November 2, 1979
47 IMP-I (IMP 7, Interplanetary Monitoring Platform-I) September 23, 1972 Magnetospheric research October 31, 1978 In orbit
48 SAS-B (Small Astronomy Satellite-B, SAS 2) November 15, 1972 X-Ray Astronomy June 8, 1973 August 20, 1980
49 RAE-B (RAE 2, Radio Astronomy Explorer-B) June 10, 1973 Radio astronomy April 26, 1977 In Lunar orbit
50 IMP J (IMP 8, Interplanetary Monitoring Platform-J) October 26, 1973 Magnetospheric research October 7, 2006 In orbit
51 AE-C (Atmosphere Explorer-C) December 16, 1973 Atmospheric research  ? December 12, 1978
52 Hawkeye 1, Injun 6 (IE-D, Ionosphere Explorer-D) June 3, 1974 Magnetospheric research April 28, 1978 April 28, 1978
53 SAS-C (Small Astronomy Satellite-C, SAS 3) May 7, 1975 X-Ray Astronomy April 7, 1979 April 9, 1979
54 AE-D (Atmosphere Explorer-D) October 6, 1975 Atmospheric research January 29, 1976 March 12, 1976
55 AE-E (Atmosphere Explorer-E) November 20, 1975 Atmospheric research September 25, 1980 June 10, 1981
56 ISEE 1 & 2 (International Sun-Earth Explorer-A & B) October 22, 1977 Magnetospheric research September 26, 1987 September 26, 1987
57 IUE January 26, 1978 Ultraviolet astronomy September 30, 1996 In orbit
58 HCMM (AEM-A, Applications Explorer Mission-A, Heat Capacity Mapping Mission) April 26, 1978 Thermal mapping of the earth September 30, 1980 December 22, 1981
59 ISEE 3 (International Sun-Earth Explorer-C, ICE) August 12, 1978 Magnetospheric research Hibernation In heliocentric orbit
60 SAGE (AEM-B, Applications Explorer Mission-B, Stratospheric Aerosol and Gas Experiment) February 18, 1979 Stratospheric aerosol and ozone data January 7, 1982 April 11, 1989
61 MAGSAT (AEM-C, Applications Explorer Mission-C, Magnetic Field Satellite) October 30, 1979 Mapped the near surface magnetic field of the Earth May 6, 1980 June 11, 1980
62 DE 1 (DE-A, Dynamics Explorer-A) August 3, 1981 Magnetospheric research February 28, 1991 In orbit
63 DE 2 (DE-B, Dynamics Explorer-B) August 3, 1981 Magnetospheric research 1983 February 19, 1983
64 SME (Solar Mesosphere Explorer) October 6, 1981 Atmospheric research April 4, 1989 March 5, 1991
65 AMTPE/CCE (Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer) August 16, 1984 Magnetospheric research July 12, 1989 In orbit
66 COBE November 18, 1989 Microwave astronomy December 23, 1993 In orbit
67 EUVE June 7, 1992 Ultraviolet astronomy January 30, 2002 January 30, 2002
68 SAMPEX July 3, 1992 Magnetospheric research June 30, 2004[6] November 13, 2012.[7]
69 RXTE December 30, 1995 X-ray astronomy January 3, 2012
Operated for 16 years
In orbit
70 FAST August 21, 1996 Auroral phenomena 2009? In orbit
71 ACE August 25, 1997 Solar/interplanetary/interstellar particle research Operational In L1 orbit
72 SNOE February 26, 1998 Atmospheric research December 13, 2003 December 13, 2003
73 TRACE April 2, 1998 Solar observatory June 21, 2010 (Hibernation)[8] In orbit
74 SWAS December 6, 1998 Submillimeter astronomy July 2004 hibernation
August 2005 after Deep Impact sub-mission
In orbit
75 WIRE March 5, 1999 Infrared astronomy, primary mission failed due to loss of coolant No Survey, limited secondary mission May 10, 2011[9]
76 TERRIERS May 18, 1999 Atmospheric research, satellite failed shortly after achieving orbit May 18, 1999 In orbit
77 FUSE June 23, 1999 Ultraviolet astronomy October 18, 2007 In orbit
78 IMAGE March 25, 2000 Magnetospheric research December 18, 2005[10] Contact lost
79 HETE-2 October 9, 2000 UV, X-Ray, and gamma ray astronomy Past[11] In orbit
80 WMAP June 30, 2001 Microwave astronomy October 2010[12] Formerly in L2 orbit. Solar Orbit
81 RHESSI February 5, 2002 X-ray and gamma ray solar flare imaging Operational In orbit
82 CHIPSat January 13, 2003 Ultraviolet spectroscopy and astronomy April 11, 2008[13] In orbit
83 GALEX April 28, 2003 Ultraviolet astronomy June 28, 2013[14] In orbit
84 SWIFT November 20, 2004 Gamma ray astronomy Operational In orbit
85 THEMIS A February 17, 2007 Magnetospheric research Operational In orbit
86 THEMIS B (ARTEMIS P1) February 17, 2007 Magnetospheric research Operational In orbit
87 THEMIS C (ARTEMIS P2) February 17, 2007 Magnetospheric research Operational In orbit
88 THEMIS D February 17, 2007 Magnetospheric research Operational In orbit
89 THEMIS E February 17, 2007 Magnetospheric research Operational In orbit
90 AIM April 25, 2007 Noctilucent cloud observation Operational In orbit
91 IBEX October 19, 2008 Mapping the boundary between the Solar System and interstellar space. Operational In orbit
92 WISE December 14, 2009 Infrared astronomy Operational In orbit
93 NuSTAR June 13, 2012 High-energy x-ray astronomy Operational In orbit
94 IRIS June 27, 2013 Solar UV astronomy Operational In orbit

Spacecraft by name[edit]

Explorer 6 on a Thor-Able III launches in August 1959
ISEE-C in a dynamic test chamber, 1978

Explorer missions in the NSSDC master catalog listing. [3] This does not include Missions of Opportunity (MO), but does include some spacecraft with launch failures or were cancelled.

Other missions[edit]

Examples of cancelled missions, include:[15]

  • Owl 1
  • Owl 2
  • MSS A
  • CATSAT (STEDI 3)
  • IMEX (UNEX 2)
  • FAME (MIDEX 4)
  • SPIDR (SMEX 8)
  • GEMS

Many more missions are proposed, but not selected. For example in 2011, the overall explorers program received 22 full missions solicitations, 20 Missions of Opportunity, and 8 USPI.[16] Another type of program called missions of opportunity (MO), which adds small missions to other spacecraft, such as an additional instrument. Examples of this include Astro-H, CINDI, TWINS, and HETE-2.

Mission endings[edit]

See also[edit]

References[edit]

External links[edit]