Encyclopedia Astronautica
Explorer


Series of satellites launched by Jet Propulsion Laboratory for the exploration of the space environment (micrometeoroids, charged particles, radiation, etc) from both earth orbital and heliocentric orbital locations.

More... - Chronology...


Associated People
  • von Braun von Braun, Wernher (1912-1977) German-American chief designer, leader of the 'Rocket Team'; developed the V-2, Redstone, Jupiter, and the Saturn rockets that took US to the moon. He made the idea of space travel popular in the 1950's and a reality in the 1960's. More...

Associated Countries
Associated Spacecraft
  • Explorer A American earth magnetosphere satellite. 3 launches, 1958.02.01 (Explorer 1) to 1958.03.26 (Explorer 3). Discovered Van Allen radiation belts. Spacecraft engaged in research and exploration of the upper atmosphere or outer space. More...
  • Explorer B American earth magnetosphere satellite. One launch, 1958.07.26, Explorer 4. Mapped project Argus radiation. More...
  • Explorer C American earth magnetosphere satellite. One launch, 1958.08.24, Explorer 5. More...
  • S-1 American earth magnetosphere satellite. 2 launches, 1959.07.16 (Explorer) to 1959.10.13 (Explorer 7). Magnetic field, solar flare data. More...
  • S-2 American earth magnetosphere satellite. One launch, 1959.08.07, Explorer 6. First Earth photo; radiation data. More...
  • S-46 American earth magnetosphere satellite. One launch, 1960.03.23, Explorer. More...
  • S-30 American earth ionosphere satellite. One launch, 1960.11.03, Explorer 8. Ionospheric research. More...
  • S-56 American earth atmosphere satellite. 2 launches, 1960.12.04 (Explorer (9) S 56) to 1961.02.16 (Explorer 9). 12 foot diameter. balloon; atmospheric density studies. More...
  • P-14 American solar satellite. 3 launches, 1961.02.24 (Explorer) to 1961.05.24 (Explorer). Magnetic field data. More...
  • S-15 American solar satellite. One launch, 1961.04.27, Explorer 11. Gamma ray data. More...
  • Injun American earth magnetosphere satellite. 5 launches, 1961.06.29 (Injun 1) to 1968.08.08 (Explorer 40). Radiation decay data satellite. May also have been a cover for some NRL ELINT satellites. More...
  • S-55 American earth micrometeoroid satellite. 4 launches, 1961.06.30 (Explorer (13) S 55) to 1964.11.06 (Explorer 23). Micrometeoroid research. More...
  • EPE American solar satellite. 4 launches, 1961.08.16 (Explorer 12) to 1964.12.21 (Explorer 26). Radiation and solar wind data. More...
  • AE American earth atmosphere satellite. 5 launches, 1963.04.03 (Explorer 17) to 1975.11.20 (Explorer 55). Atmospheric research. More...
  • IMP American earth magnetosphere satellite. 10 launches, 1963.11.27 (Explorer 18) to 1973.10.26 (Explorer 50). More...
  • ADE American earth atmosphere satellite. 3 launches, 1963.12.19 (Explorer 19) to 1968.08.08 (Explorer 39). 12 foot diameter. balloon; identical to Explorer 9; atmospheric density studies. More...
  • BE American earth magnetosphere satellite. One launch, 1964.03.19, Explorer (20). Also known as Explorer S-66. More...
  • IE American earth ionosphere satellite. One launch, 1964.08.25, Explorer 20. Ionospheric research. More...
  • Beacon American earth ionosphere satellite. 2 launches, 1964.10.10 (Explorer 22) to 1965.04.29 (Explorer 27). Early technology satellite. None reached orbit. More...
  • GEOS American solar satellite. 3 launches, 1965.11.06 (Explorer 29) to 1975.04.09 (Geos 3). The GEOS spacecraft were gravity-gradient-stabilized, solar-cell powered satellites designed exclusively for geodetic studies. More...
  • IQSY American solar satellite. One launch, 1965.11.19, Explorer 30. Solar radiation data. More...
  • DME American earth ionosphere satellite. One launch, 1965.11.29, Explorer 31. Explorer 31, the Direct Measurement Explorer, was launched with a Canadian Alouette II on November 28, 1965, on a Thor-Agena rocket from Vandenberg Air Force Base, California. More...
  • Solrad American solar satellite. 4 launches, 1968.03.05 (Explorer 37) to 1976.03.15 (Solrad 11B). SOLRAD was Satellite Techniques' first major project and NRL's first post-Vanguard satellite. More...
  • RAE American radio astronomy satellite. 2 launches, 1968.07.04 (Explorer 38) to 1973.06.10 (Explorer 49). More...
  • SAS Italian solar satellite. 3 launches, 1970.12.12 (Explorer 42) to 1975.05.07 (Explorer 53). More...
  • SSS American earth magnetosphere satellite. One launch, 1971.11.15, Explorer 45. Studies magnetosphere, energetic particles. More...
  • MTS American earth micrometeoroid satellite. One launch, 1972.08.13, Explorer 46. Micrometeoroid tests. More...
  • Hawkeye American solar satellite. One launch, 1974.06.03, Explorer 52. Solar wind experiments. Follow-on to Injun. More...
  • DAD American earth atmosphere satellite. 2 launches, 1975.12.06 (DAD-B) and (DAD-B). Dual Air Density; air density experiments. More...

See also
Associated Launch Vehicles
  • Jupiter C American orbital launch vehicle. Re-entry vehicle test booster and satellite launcher derived from Redstone missile. The Jupiter A version of the Redstone missile was modified with upper stages to test Jupiter re-entry vehicle configurations. Von Braun's team was ordered to ballast the upper stage with sand to prevent any 'inadvertent' artificial satellites from stealing thunder from the official Vanguard program. Korolev's R-7 orbited the first earth satellite instead. The Jupiter C was retroactively named the 'Juno I' by Von Braun's team. More...
  • Juno II American orbital launch vehicle. Satellite launcher derived from Jupiter IRBM. Basic 4 stage vehicle consisted of 1 x Jupiter + 1 x Cluster stage 2 + 1 x Cluster stage 3 + 1 x RTV Motor More...
  • Thor Able III American orbital launch vehicle. Three stage vehicle consisting of 1 x Thor DM-18A + 1 x Able 3/AJ10 + 1 x Altair More...
  • Thor Delta American orbital launch vehicle. Commercial name for the military's Thor-Delta. The name of the Delta second stage eventually was applied to subsequent commercial follow-ons. More...
  • Scout X-1 American all-solid orbital launch vehicle. Four stage vehicle consisting of 1 x Algol 1B + 1 x Castor + 1 x Antares + 1 x Altair More...
  • Delta A American orbital launch vehicle. Three stage vehicle consisting of 1 x Thor DM-21 + 1 x AJ10-118 + 1 x Altair More...
  • Delta B American orbital launch vehicle. Three stage vehicle consisting of 1 x Thor DM-21 + 1 x AJ10-118A + 1 x Altair More...
  • Scout X-3 American all-solid orbital launch vehicle. Four stage vehicle consisting of 1 x Algol 2A + 1 x Castor + 1 x Antares 2 + 1 x Altair More...
  • Scout X-4 American all-solid orbital launch vehicle. Four stage vehicle consisting of 1 x Algol 2A + 1 x Castor + 1 x Antares 2 + 1 x Altair 2 More...
  • Thor Delta C American orbital launch vehicle. Three stage vehicle consisting of 1 x Thor DSV-2A + 1 x Delta D + 1 x Altair 2 More...
  • Scout B American all-solid orbital launch vehicle. Four stage vehicle consisting of 1 x Algol 2B + 1 x Castor 2 + 1 x Antares 2 + 1 x FW4S More...
  • Delta E American orbital launch vehicle. Thor augmented with 3 x Castor 2 motors with Delta E and Altair 2 upper stage. More...
  • Thor Delta C1 American orbital launch vehicle. Three stage vehicle consisting of 1 x Thor DSV-2A + 1 x Delta D + 1 x FW4D More...
  • Delta E1 American orbital launch vehicle. Four stage vehicle consisting of 3 x Castor + 1 x Thor DSV-2C + 1 x Delta E + 1 x FW4D More...
  • Delta J American orbital launch vehicle. Four stage vehicle consisting of 3 x Castor + 1 x Thor DSV-2C + 1 x Delta E + 1 x Star 37D More...
  • Delta M6 American orbital launch vehicle. Four stage vehicle consisting of 6 x Castor 2 + 1 x LT Thor DSV-2L-1C + 1 x Delta E + 1 x Star 37D More...
  • Scout D-1 American all-solid orbital launch vehicle. Four stage vehicle consisting of 1 x Algol 3A + 1 x Castor 2 + 1 x Antares 2 + 1 x Star 20 More...
  • Delta 1604 American orbital launch vehicle. Four stage vehicle consisting of 6 x Castor 2 + 1 x ELT Thor/MB-3 + 1 x Delta F + 1 x Star 37C More...
  • Delta 1913 American orbital launch vehicle. Four stage vehicle consisting of 9 x Castor 2 + 1 x ELT Thor/MB-3 + 1 x Delta P /TR-201 + 1 x Star 37D More...
  • Delta 1900 American orbital launch vehicle. Three stage vehicle consisting of 9 x Castor 2 + 1 x ELT Thor/MB-3 + 1 x Delta F More...
  • Scout E-1 American all-solid orbital launch vehicle. Five stage vehicle consisting of 1 x Algol 3A + 1 x Castor 2 + 1 x Antares 2 + 1 x FW4S + 1 x BE-3 More...
  • Delta 2910 American orbital launch vehicle. Three stage vehicle consisting of 9 x Castor 2 + 1 x ELT Thor/RS-27 + 1 x Delta P /TR-201 More...
  • Scout F American all-solid orbital launch vehicle. Four stage vehicle consisting of 1 x Algol 3A + 1 x Castor 2 + 1 x Antares 2B + 1 x Star 20 More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • NRL American manufacturer of rockets and spacecraft. Naval Research Laboratory, Washington, DC, USA. More...
  • USAF American agency overseeing development of rockets and spacecraft. United States Air Force, USA. More...
  • DARPA American agency overseeing development of rockets and spacecraft. Defense Advanced Research Projects Agency (formerly ARPA), USA. More...
  • NASA Langley American agency overseeing development of rockets and spacecraft. Langley, USA. More...
  • AFSC American agency. Air Force Systems Command, USA. More...

Associated Launch Sites
  • Wallops Island Small NASA launch site for sounding rocket launches and occasional Scout launches to orbit. Air launches are conducted from the Drop Zone Wallops Island, 37.00 N 72.0 W. With the last orbital launch in 1985 and the decline in sounding rocket launches, Wallops fell into near-disuse as a launch center. Its fortunes revised with the establishment of Mid-Atlantic Regional Spaceport in 2005 and orbital launches resumed in 2010. More...
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Vandenberg Vandenberg Air Force Base is located on the Central Coast of California about 240 km northwest of Los Angeles. It is used for launches of unmanned government and commercial satellites into polar orbit and intercontinental ballistic missile test launches toward the Kwajalein Atoll. More...
  • San Marco In 1962 NASA signed an agreement with the Centro Ricerche Aerospaziali at the University of Rome creating the San Marco program. The purpose of the program was to place an Italian satellite in orbit and to create an Italian equatorial launch site for the Scout rocket. Permission was obtained from Kenya to emplace two modified oil platforms off their coast, on the equator. The Santa Rita platform would serve as a launch control center and would also be used for launch of sounding rockets. The San Marco platform would be dedicated to launch of Scout rockets to orbit. More...

Explorer Chronology


1950 April 15 - .
  • Missile development moved to Redstone Arsenal. - . Nation: USA. Program: Explorer. Summary: Peenemuende team moved from White Sands to Huntsville.

1954 August 15 - . LV Family: Redstone. Launch Vehicle: Jupiter C.
  • Von Braun proposes launch of US satellite. - . Payload: Explorer A. Nation: USA. Related Persons: von Braun. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer A. Summary: Von Braun report 'A Minimum Satellite Vehicle Based on Components Available from Developments of the Army Ordnance Corps' in response to June Pentagon meeting proposes $ 100,000 to launch satellite by Redstone..

1955 August 24 - . LV Family: Redstone. Launch Vehicle: Jupiter C.
  • Redstone recommended as satellite launcher. - . Payload: Explorer A. Nation: USA. Related Persons: von Braun. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer A. Research and development Policy Council (DOD) unanimously recommended that the time-risk factor in the scientific satellite program be brought to the attention of the Secretary of the Defense for determination as to whether a Redstone backup program was indicated.

1957 October 5 - . LV Family: Redstone. Launch Vehicle: Jupiter C.
  • Von Braun promises first US satellite in 60 days. - . Payload: Explorer A. Nation: USA. Related Persons: von Braun; McElroy; Medaris. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer A. Summary: Von Braun briefs Secretary of Defence McElroy on Jupiter-C/Redstone for immediate US satellite launch. Promises launch in 60 days. Medaris says 90..

1957 November 8 - . LV Family: Redstone. Launch Vehicle: Jupiter C.
  • Von Braun ordered to launch satellite. - . Nation: USA. Related Persons: von Braun; McElroy. Program: Explorer. Secretary of Defense Neil McElroy directed the Army to proceed with the launching of the Explorer earth satellites. This order, in effect, resumed the Orbiter project that had been eliminated from the IGY satellite planning program on September 9, 1955. Von Braun was to modify two Jupiter-C missiles (modified Redstones) and attempt to place an artificial earth satellite in orbit by March 58.

1958 February 1 - . 03:47 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26A. LV Family: Redstone. Launch Vehicle: Jupiter C. LV Configuration: Jupiter C/Juno I RS-29.
  • Explorer 1 - . Payload: Explorer A. Mass: 5.00 kg (11.00 lb). Nation: USA. Related Persons: von Braun. Agency: USA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer A. Decay Date: 1970-03-31 . USAF Sat Cat: 4 . COSPAR: 1958-Alpha-1. Apogee: 1,859 km (1,155 mi). Perigee: 347 km (215 mi). Inclination: 33.2000 deg. Period: 107.20 min. Explorer I, the first U.S. earth satellite, was launched by a modified Army Ballistic Missile Agency Jupiter-C. Explorer I, developed by the Jet Propulsion Laboratory, carried the U.S.-IGY (International Geophysical Year) experiment of James A. Van Allen and resulted in the discovery of the radiation belt around the earth.

1958 March 5 - . 18:27 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26A. LV Family: Redstone. Launch Vehicle: Jupiter C. LV Configuration: Jupiter C/Juno I RS/CC-26. FAILURE: Fourth Stage failed to ignite.. Failed Stage: 4.
  • Explorer 2 - . Payload: Explorer A. Mass: 5.00 kg (11.00 lb). Nation: USA. Related Persons: von Braun. Agency: USA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer A. Decay Date: 1958-03-05 . COSPAR: F580305A.

1958 March 26 - . 17:38 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC5. LV Family: Redstone. Launch Vehicle: Jupiter C. LV Configuration: Jupiter C/Juno I RS-24.
  • Explorer 3 - . Payload: Explorer A. Mass: 5.00 kg (11.00 lb). Nation: USA. Related Persons: von Braun. Agency: USA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer A. Decay Date: 1958-06-28 . USAF Sat Cat: 6 . COSPAR: 1958-Gamma-1. Apogee: 2,799 km (1,739 mi). Perigee: 186 km (115 mi). Inclination: 33.4000 deg. Period: 115.70 min. Summary: Radiation, micrometeoroid data. .

1958 July 26 - . 15:00 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC5. LV Family: Redstone. Launch Vehicle: Jupiter C. LV Configuration: Jupiter C/Juno I RS/CC-44.
  • Explorer 4 - . Payload: Explorer B. Mass: 8.00 kg (17.60 lb). Nation: USA. Related Persons: von Braun. Agency: DARPA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer B. Decay Date: 1959-10-23 . USAF Sat Cat: 9 . COSPAR: 1958-Epsilon-1. Apogee: 1,352 km (840 mi). Perigee: 257 km (159 mi). Inclination: 50.2000 deg. Period: 100.90 min. Summary: Mapped project Argus radiation. .

1958 August 24 - . 06:17 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC5. LV Family: Redstone. Launch Vehicle: Jupiter C. LV Configuration: Jupiter C/Juno I RS/CC-47. FAILURE: First Stage collided with upper stages. Second Stage ignited in wrong direction.. Failed Stage: 2.
  • Explorer 5 - . Payload: Explorer C. Mass: 17 kg (37 lb). Nation: USA. Related Persons: von Braun. Agency: DARPA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Explorer C. Decay Date: 1958-08-24 . COSPAR: F580824A.

1959 July 16 - . 17:37 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC5. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-16. FAILURE: Control lost after 5.5 sec. Destroyed by range safety.. Failed Stage: 1.
  • Explorer S-1 - . Payload: S-1. Mass: 41 kg (90 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: S-1. Decay Date: 1959-07-16 . COSPAR: F590716A.

1959 August 7 - . 14:24 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Thor Able III. LV Configuration: Thor Able III 134.
  • Explorer 6 - . Payload: S-2. Mass: 64 kg (141 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: S-2. Decay Date: 1961-06-30 . USAF Sat Cat: 15 . COSPAR: 1959-Delta-1. Apogee: 42,400 km (26,300 mi). Perigee: 245 km (152 mi). Inclination: 47.0000 deg. Period: 765.00 min. Summary: First Earth photo; radiation data..

1959 October 13 - . 15:30 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC5. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-19A.
  • Explorer 7 - . Payload: S-1A. Mass: 42 kg (92 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: S-1. USAF Sat Cat: 22 . COSPAR: 1959-Iota-1. Apogee: 857 km (532 mi). Perigee: 523 km (324 mi). Inclination: 50.3000 deg. Period: 98.60 min. Summary: Spacecraft engaged in research and exploration of the upper atmosphere or outer space. Returned magnetic field and solar flare data..

1960 March 23 - . 13:35 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26B. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-19C. FAILURE: Upper stage failed to ignite. Third stage failed to ignite due to loss of radio contact.. Failed Stage: 3.
  • Explorer S-46 - . Payload: S-46. Mass: 16 kg (35 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: S-46. Decay Date: 1960-03-23 . COSPAR: F600323A.

1960 November 3 - . 05:23 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26B. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-19D.
  • Explorer 8 - . Payload: S-30. Mass: 41 kg (90 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Ionosphere satellite. Spacecraft: S-30. USAF Sat Cat: 60 . COSPAR: 1960-Xi-1. Apogee: 1,331 km (827 mi). Perigee: 394 km (244 mi). Inclination: 49.9000 deg. Period: 102.20 min. Summary: Ionospheric research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1960 December 4 - . 21:14 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3. LV Family: Scout. Launch Vehicle: Scout X-1. LV Configuration: Scout X-1 ST-3. FAILURE: Second stage malfunction.. Failed Stage: 2.
  • Explorer (9) S 56 - . Payload: S-56. Mass: 6.00 kg (13.20 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: S-56. Decay Date: 1960-12-04 . COSPAR: F601204A.

1961 February 16 - . 13:05 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3. LV Family: Scout. Launch Vehicle: Scout X-1. LV Configuration: Scout X-1 ST-4.
  • Explorer 9 - . Payload: S-56A. Mass: 7.00 kg (15.40 lb). Nation: USA. Agency: USAF. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: S-56. Decay Date: 1964-04-09 . USAF Sat Cat: 81 . COSPAR: 1961-Delta-1. Apogee: 2,433 km (1,511 mi). Perigee: 757 km (470 mi). Inclination: 38.8000 deg. Period: 118.00 min. Summary: 12 foot dia. balloon; atmospheric density studies. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1961 February 25 - . 00:13 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26B. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-19F. FAILURE: Third Stage failed to ignite.. Failed Stage: 3.
  • Explorer - . Payload: S-45. Mass: 34 kg (74 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: P-14. Decay Date: 1961-02-24 . COSPAR: F610224A.

1961 March 25 - . 15:17 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Thor Delta. LV Configuration: Thor Delta 295/D4.
  • Explorer 10 - . Payload: P-14. Mass: 35 kg (77 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: P-14. Decay Date: 1961-06-30 . USAF Sat Cat: 98 . COSPAR: 1961-Kappa-1. Apogee: 181,100 km (112,500 mi). Perigee: 221 km (137 mi). Inclination: 33.0000 deg. Period: 5,013.90 min. Summary: Magnetic field data. Decay date suspect Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B)..

1961 April 27 - . 14:16 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26B. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-19E.
  • Explorer 11 - . Payload: S-15. Mass: 37 kg (81 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: S-15. USAF Sat Cat: 107 . COSPAR: 1961-Nu-1. Apogee: 1,458 km (905 mi). Perigee: 480 km (290 mi). Inclination: 28.8000 deg. Period: 104.50 min. Summary: Gamma ray data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1961 May 24 - . 19:48 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC26B. LV Family: Jupiter. Launch Vehicle: Juno II. LV Configuration: Juno II AM-19G. FAILURE: Second Stage failed to ignite.. Failed Stage: 2.
  • Explorer S-45A - . Payload: S-45A. Mass: 33 kg (72 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: P-14. Decay Date: 1961-05-24 . COSPAR: F610524A.

1961 June 30 - . 17:09 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3. LV Family: Scout. Launch Vehicle: Scout X-1. LV Configuration: Scout X-1 ST-5. FAILURE: Third stage did not ignite, and the vehicle was destroyed.. Failed Stage: 3.
  • Explorer (13) S 55 - . Payload: S-55. Mass: 84 kg (185 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Micrometeoroid satellite. Spacecraft: S-55. Decay Date: 1961-06-30 . COSPAR: F610630A. Apogee: 172 km (106 mi). Summary: Micrometeorite counter satellite (S-55)..

1961 August 16 - . 03:21 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Thor Delta. LV Configuration: Thor Delta 312/D6.
  • Explorer 12 - . Payload: EPE A (S-3). Mass: 38 kg (83 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: EPE. Decay Date: 1963-08-31 . USAF Sat Cat: 170 . COSPAR: 1961-Upsilon-1. Apogee: 76,620 km (47,600 mi). Perigee: 790 km (490 mi). Inclination: 33.4000 deg. Period: 1,587.30 min. Summary: Radiation and solar wind data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1961 August 25 - . 18:29 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3. LV Family: Scout. Launch Vehicle: Scout X-1. LV Configuration: Scout X-1 ST-6. FAILURE: Partial Failure.. Failed Stage: 4.
  • Explorer 13 - . Payload: S-55A. Mass: 86 kg (189 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Micrometeoroid satellite. Spacecraft: S-55. Decay Date: 1961-08-28 . USAF Sat Cat: 180 . COSPAR: 1961-Chi-1. Apogee: 1,164 km (723 mi). Perigee: 125 km (77 mi). Inclination: 37.7000 deg. Period: 97.50 min. Summary: Useless orbit; micrometeoroid research. Partial Failure..

1962 October 2 - . 22:11 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta A. LV Configuration: Thor Delta A 345/D13.
  • Explorer 14 - . Payload: EPE B (S-3A). Mass: 40 kg (88 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: EPE. Decay Date: 1964-12-31 . USAF Sat Cat: 432 . COSPAR: 1962-B-Gamma-1. Apogee: 96,229 km (59,793 mi). Perigee: 2,558 km (1,589 mi). Inclination: 42.3000 deg. Period: 2,184.60 min. Summary: Magnetosphere studies. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1962 October 27 - . 23:15 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta A. LV Configuration: Thor Delta A 346/D14.
  • Explorer 15 - . Payload: EPE C (S-3C SERB). Mass: 45 kg (99 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: EPE. Decay Date: 1978-12-19 . USAF Sat Cat: 445 . COSPAR: 1962-B-Lambda-1. Apogee: 17,610 km (10,940 mi). Perigee: 306 km (190 mi). Inclination: 17.9000 deg. Period: 314.70 min. Summary: Radiation decay data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1962 December 16 - . 14:33 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3. LV Family: Scout. Launch Vehicle: Scout X-3. LV Configuration: Scout X-3 S115.
  • Explorer 16 - . Payload: S-55B. Mass: 100 kg (220 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Micrometeoroid satellite. Spacecraft: S-55. USAF Sat Cat: 506 . COSPAR: 1962-B-Chi-1. Apogee: 1,159 km (720 mi). Perigee: 744 km (462 mi). Inclination: 52.0000 deg. Period: 104.10 min. Summary: Micrometeoroid data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1963 April 3 - . 02:00 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta B. LV Configuration: Thor Delta B 357/D17.
  • Explorer 17 - . Payload: AE A (S-6). Mass: 185 kg (407 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: AE. Decay Date: 1966-11-24 . USAF Sat Cat: 564 . COSPAR: 1963-009A. Apogee: 891 km (553 mi). Perigee: 254 km (157 mi). Inclination: 57.6000 deg. Period: 96.10 min. Summary: Atmospheric research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1963 November 27 - . 02:30 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Thor Delta C. LV Configuration: Thor Delta C 387/D21.
  • Explorer 18 - . Payload: IMP A. Mass: 62 kg (136 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. Decay Date: 1965-11-30 . USAF Sat Cat: 693 . COSPAR: 1963-046A. Apogee: 197,616 km (122,792 mi). Perigee: 192 km (119 mi). Inclination: 33.3000 deg. Period: 5,666.20 min. Summary: Radiation data; Interplanetary Monitoring Program. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1963 December 19 - . 18:49 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S122R.
  • Explorer 19 - . Payload: ADE A. Mass: 7.00 kg (15.40 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: ADE. Decay Date: 1981-05-10 . USAF Sat Cat: 714 . COSPAR: 1963-053A. Apogee: 2,391 km (1,485 mi). Perigee: 597 km (370 mi). Inclination: 78.6000 deg. Period: 115.90 min. Summary: 12 foot dia. balloon; identical to Explorer 9; atmospheric density studies. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1964 March 19 - . 11:13 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta B. LV Configuration: Thor Delta B 391/D24. FAILURE: Insufficient third stage thrust.. Failed Stage: 3.
  • Explorer (20) - . Payload: Beacon Explorer A. Mass: 54 kg (119 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: BE. Decay Date: 1964-03-19 . COSPAR: F640319A. Summary: Also known as Explorer S-66..

1964 August 25 - . 13:43 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S134R.
  • Explorer 20 - . Payload: IE A (S-48 Ionosphere Explorer). Mass: 44 kg (97 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Ionosphere satellite. Spacecraft: IE. USAF Sat Cat: 870 . COSPAR: 1964-051A. Apogee: 999 km (620 mi). Perigee: 857 km (532 mi). Inclination: 79.9000 deg. Period: 103.60 min. Summary: Ionospheric research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B)..

1964 October 4 - . 03:45 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Thor Delta C. LV Configuration: Thor Delta C 392/D26.
  • Explorer 21 - . Payload: IMP B. Mass: 62 kg (136 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. Decay Date: 1965-12-31 . USAF Sat Cat: 889 . COSPAR: 1964-060A. Apogee: 95,590 km (59,390 mi). Perigee: 191 km (118 mi). Inclination: 33.5000 deg. Period: 2,097.00 min. Summary: Lower than planned orbit. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1964 October 10 - . 03:00 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S123R.
  • Explorer 22 - . Payload: Beacon Explorer B. Mass: 52 kg (114 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Ionosphere satellite. Spacecraft: Beacon. USAF Sat Cat: 899 . COSPAR: 1964-064A. Apogee: 1,053 km (654 mi). Perigee: 872 km (541 mi). Inclination: 79.7000 deg. Period: 104.30 min. Summary: Ionospheric and geodetic data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space..

1964 November 6 - . 12:02 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S133R.
  • Explorer 23 - . Payload: S-55C. Mass: 134 kg (295 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Micrometeoroid satellite. Spacecraft: S-55. Decay Date: 1983-06-29 . USAF Sat Cat: 924 . COSPAR: 1964-074A. Apogee: 980 km (600 mi). Perigee: 463 km (287 mi). Inclination: 51.9000 deg. Period: 99.20 min. Summary: Micrometeoroid data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1964 November 21 - . 17:09 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S135R.
  • Explorer 24 - . Payload: ADE B. Mass: 9.00 kg (19.80 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: ADE. Decay Date: 1968-10-18 . USAF Sat Cat: 931 . COSPAR: 1964-076A. Apogee: 2,498 km (1,552 mi). Perigee: 530 km (320 mi). Inclination: 81.4000 deg. Period: 116.30 min. Summary: 12 foot dia. balloon; atmospheric density studies. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .
  • Explorer 25 - . Payload: Injun 4. Mass: 40 kg (88 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Injun. USAF Sat Cat: 932 . COSPAR: 1964-076B. Apogee: 2,319 km (1,440 mi). Perigee: 526 km (326 mi). Inclination: 81.3000 deg. Period: 114.30 min. Summary: Radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1964 December 21 - . 09:00 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Thor Delta C. LV Configuration: Thor Delta C 393/D27.
  • Explorer 26 - . Payload: EPE D - 661A Flight 21-3. Mass: 46 kg (101 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: EPE. Decay Date: 1978-03-31 . USAF Sat Cat: 963 . COSPAR: 1964-086A. Apogee: 10,043 km (6,240 mi). Perigee: 284 km (176 mi). Inclination: 19.8000 deg. Period: 205.70 min. Summary: Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B)..

1965 April 29 - . 14:17 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3A. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S136R.
  • Explorer 27 - . Payload: Beacon Explorer C. Mass: 60 kg (132 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Ionosphere satellite. Spacecraft: Beacon. USAF Sat Cat: 1328 . COSPAR: 1965-032A. Apogee: 1,309 km (813 mi). Perigee: 932 km (579 mi). Inclination: 41.2000 deg. Period: 107.70 min. Summary: Battery failed in 1968; ionospheric research and geodetic data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space..

1965 May 29 - . 12:00 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Thor Delta C. LV Configuration: Thor Delta C 441/D31.
  • Explorer 28 - . Payload: IMP C. Mass: 58 kg (127 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. Decay Date: 1968-07-04 . USAF Sat Cat: 1388 . COSPAR: 1965-042A. Apogee: 261,206 km (162,305 mi). Perigee: 229 km (142 mi). Inclination: 30.5000 deg. Period: 8,419.70 min. Summary: Magnetic field, radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1965 November 6 - . 18:38 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta E. LV Configuration: Thor Delta E 457/D34.
  • Explorer 29 - . Payload: GEOS A. Mass: 175 kg (385 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: GEOS. USAF Sat Cat: 1726 . COSPAR: 1965-089A. Apogee: 2,269 km (1,409 mi). Perigee: 1,120 km (690 mi). Inclination: 59.4000 deg. Period: 120.30 min. The primary objective of GEOS-A was to provide global geodetic measurements for determining the positions of fiducial control points on the Earth to an accuracy of 10 meters in an Earth centre of mass co-ordinate system, and to determine the structure of the Earth's gravity field to 5 parts in 10 million. Instrumentation included (1) four optical beacons, (2) laser reflectors, (3) a radio range transponder, (4) Doppler beacons, and (5) a range and range rate transponder. These were designed to operate simultaneously to fulfil the objectives of locating observation points (geodetic control stations) in a three dimensional earth centre-of-mass co-ordinate system within 10 m of accuracy, of defining the structure of the earth's irregular gravitational field and refining the locations and magnitudes of the large gravity anomalies, and of comparing results of the various systems onboard the spacecraft to determine the most accurate and reliable system. In January 1967, a failure in the satellite's command system rendered several geodetic systems inoperable. Radio doppler measurements and the passive laser reflector experiment could continue indefinitely, however. Additional Details: here....

1965 November 19 - . 04:48 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3A. LV Family: Scout. Launch Vehicle: Scout X-4. LV Configuration: Scout X-4 S138R.
  • Explorer 30 - . Payload: Solar Explorer A. Mass: 57 kg (125 lb). Nation: USA. Agency: NRL. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: IQSY. USAF Sat Cat: 1738 . COSPAR: 1965-093A. Apogee: 856 km (531 mi). Perigee: 671 km (416 mi). Inclination: 59.7000 deg. Period: 100.10 min. Summary: Solar radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1965 November 29 - . 04:48 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2E. LV Family: Delta. Launch Vehicle: Thor Agena B SLV-2. LV Configuration: Thor SLV-2A Agena B 453 (TA5) / Agena B S-01 6102 .
  • Explorer 31 - . Payload: DME A. Mass: 99 kg (218 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Ionosphere satellite. Spacecraft: DME. USAF Sat Cat: 1806 . COSPAR: 1965-098B. Apogee: 2,833 km (1,760 mi). Perigee: 505 km (313 mi). Inclination: 79.8000 deg. Period: 119.70 min. Ionospheric research; data correlated with Alouette 2. The Explorer 31, Direct Measurement Explorer, was launched with a Canadian Alouette II on November 28, 1965, on a Thor-Agena rocket from Vandenberg Air Force Base, California. The double-launch project, known as ISIS-X was the first in a new co-operative NASA-Canadian Defense Research Board program for International Satellites for Ionospheric Studies. Explorer 31 was in orbit with an apogee just over a kilometre more than Alouette's and with a perigee of just more than a kilometre lower. The orbits were some 3000 km at apogee and 500 km at perigee. Eight ionospheric measurement experiments sampled the environment both forward and after the satellite's path.

1966 May 25 - . 14:00 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Thor Delta C1. LV Configuration: Thor Delta C1 436/D38.
  • Explorer 32 - . Payload: AE B. Mass: 225 kg (496 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: AE. Decay Date: 1985-02-22 . USAF Sat Cat: 2183 . COSPAR: 1966-044A. Apogee: 2,723 km (1,691 mi). Perigee: 282 km (175 mi). Inclination: 64.6000 deg. Period: 116.00 min. Summary: Atmospheric Explorer; aeronomy experiments. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1966 July 1 - . 16:02 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta E1. LV Configuration: Thor Delta E1 467/D39.
  • Explorer 33 - . Payload: AIMP D. Mass: 93 kg (205 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. USAF Sat Cat: 2258 . COSPAR: 1966-058A. Apogee: 480,762 km (298,731 mi). Perigee: 265,679 km (165,084 mi). Inclination: 24.1000 deg. Period: 38,792.40 min. Summary: Intended to enter lunar orbit. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1967 May 24 - . 14:05 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2E. LV Family: Delta. Launch Vehicle: Delta E1. LV Configuration: Thor Delta E1 486/D49.
  • Explorer 34 - . Payload: IMP F. Mass: 75 kg (165 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. Decay Date: 1969-05-03 . USAF Sat Cat: 2817 . COSPAR: 1967-051A. Apogee: 214,379 km (133,208 mi). Perigee: 242 km (150 mi). Inclination: 67.1000 deg. Period: 6,358.20 min. Summary: Radiation, magnetic field data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1967 July 19 - . 14:19 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta E1. LV Configuration: Thor Delta E1 488/D50.
  • Explorer 35 - . Payload: AIMP E. Mass: 104 kg (229 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. USAF Sat Cat: 2884 . COSPAR: 1967-070A. Apogee: 675 km (419 mi). Perigee: 484 km (300 mi). Inclination: 32.4000 deg. Period: 96.26 min. Earth magnetic tail measurements. Lunar Orbit (Selenocentric). The Westinghouse Aerospace Division, under contract to National Aeronautics and Space Administration's Goddard Space Flight Center, engaged in the system design, integration, assembly and launch support for Anchored Interplanetary Monitoring Platform Satellite, officially designated Explorer 35 by the National Aeronautics and Space Administration. It was launched on July 19, 1967, with the primary objectives of investigation of interplanetary plasma and the interplanetary magnetic field out to and at the lunar distance, in either a captured lunar orbit or a geocentric orbit of the earth. In the geocentric orbit, the apogee was near or beyond the lunar distance. In a lunar orbit, additional objectives included obtaining data on dust distribution, lunar gravitational field, ionosphere, magnetic field, and radiation environment around the moon. AIMP-E also studied spatial and temporal relationships of geophysical and interplanetary phenomena simultaneously being studied by several other National Aeronautics and Space Administration satellites. The investigation in the vicinity of the moon provided for measurements of the characteristics of the interplanetary dust distribution, solar and galactic cosmic rays, as well as a study of the magnetohydrodynamic wake of the earth in the interplanetary medium at the lunar distances.

1968 January 11 - . 16:16 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2E. LV Family: Delta. Launch Vehicle: Delta E1. LV Configuration: Thor Delta E1 454/D56.
  • Explorer 36 - . Payload: GEOS B. Mass: 209 kg (460 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: GEOS. USAF Sat Cat: 3093 . COSPAR: 1968-002A. Apogee: 1,574 km (978 mi). Perigee: 1,081 km (671 mi). Inclination: 105.8000 deg. Period: 112.20 min. The geodetic instrumentation systems included (1) four optical beacons, (2) two C-band radar transponders, (3) a passive radar reflector, (4) a sequential collation of range radio range transponder, (5) a Goddard range and range rate transponder, (6) laser reflectors, and (7) Doppler beacons. Non-geodetic systems included a laser detector and a Minitrack interferometer beacon. The objectives of the spacecraft were to optimise optical station visibility periods and to provide complementary data for inclination-dependent terms established by the Explorer 29 (GEOS 1) gravimetric studies. The spacecraft was placed into a retrograde orbit to accomplish these objectives. Operational problems occurred in the main power system, optical beacon flash system, and the spacecraft clock, and adjustments in scheduling resulted in nominal operations.

1968 March 5 - . 18:28 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3A. LV Family: Scout. Launch Vehicle: Scout B. LV Configuration: Scout B S160C. FAILURE: Partial Failure.. Failed Stage: 4.
  • Explorer 37 - . Payload: Solar Explorer B. Mass: 198 kg (436 lb). Nation: USA. Agency: NRL. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: Solrad. Decay Date: 1990-11-16 . USAF Sat Cat: 3141 . COSPAR: 1968-017A. Apogee: 433 km (269 mi). Perigee: 353 km (219 mi). Inclination: 59.3000 deg. Period: 92.40 min. Summary: Solar Explorer B; radiation data; off-nominal orbit..

1968 July 4 - . 17:26 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2E. LV Family: Delta. Launch Vehicle: Delta J. LV Configuration: Thor Delta J 476/D57.
  • Explorer 38 - . Payload: RAE A. Mass: 190 kg (410 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: X-ray astronomy satellite. Spacecraft: RAE. USAF Sat Cat: 3307 . COSPAR: 1968-055A. Apogee: 5,861 km (3,641 mi). Perigee: 5,835 km (3,625 mi). Inclination: 120.9000 deg. Period: 224.30 min. Summary: Radio Astronomy Explorer; Earth, solar, cosmic radio emission data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1968 August 8 - . 20:12 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout B. LV Configuration: Scout B S165C.
  • Explorer 39 - . Payload: ADE C. Mass: 9.00 kg (19.80 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: ADE. Decay Date: 1981-06-22 . USAF Sat Cat: 3337 . COSPAR: 1968-066A. Apogee: 2,538 km (1,577 mi). Perigee: 670 km (410 mi). Inclination: 80.7000 deg. Period: 118.30 min. Summary: Air Density Explorer; atmospheric density and temperature data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .
  • Explorer 40 - . Payload: Injun E. Mass: 70 kg (154 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Injun. USAF Sat Cat: 3338 . COSPAR: 1968-066B. Apogee: 2,489 km (1,546 mi). Perigee: 679 km (421 mi). Inclination: 80.7000 deg. Period: 117.80 min. Summary: Injun Explorer; radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1969 June 21 - . 08:47 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2W. LV Family: Delta. Launch Vehicle: Delta E1. LV Configuration: Thor Delta E1 482/D69.
  • Explorer 41 - . Payload: IMP G. Mass: 174 kg (383 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. Decay Date: 1972-12-23 . USAF Sat Cat: 3990 . COSPAR: 1969-053A. Apogee: 98,159 km (60,993 mi). Perigee: 80,374 km (49,941 mi). Inclination: 86.0000 deg. Period: 4,906.30 min. Summary: Cislunar radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1970 December 12 - . 10:53 GMT - . Launch Site: San Marco. LV Family: Scout. Launch Vehicle: Scout B. LV Configuration: Scout B S175C.
  • Explorer 42 - . Payload: SAS A. Mass: 143 kg (315 lb). Nation: Italy. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: SAS. Decay Date: 1979-04-05 . USAF Sat Cat: 4797 . COSPAR: 1970-107A. Apogee: 570 km (350 mi). Perigee: 521 km (323 mi). Inclination: 3.0000 deg. Period: 95.50 min. Summary: Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1971 March 13 - . 16:15 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta M6. LV Configuration: Thor Delta M6 562/D83.
  • Explorer 43 - . Payload: IMP I. Mass: 288 kg (634 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. Decay Date: 1974-10-02 . USAF Sat Cat: 5043 . COSPAR: 1971-019A. Apogee: 203,130 km (126,210 mi). Perigee: 1,845 km (1,146 mi). Inclination: 31.2000 deg. Period: 5,957.90 min. Summary: Earth magnetosphere research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1971 July 8 - . 22:58 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3A. LV Family: Scout. Launch Vehicle: Scout B. LV Configuration: Scout B S177C.
  • Explorer 44 - . Payload: Solar Explorer C. Mass: 118 kg (260 lb). Nation: USA. Agency: NRL. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: Solrad. Decay Date: 1979-12-15 . USAF Sat Cat: 5317 . COSPAR: 1971-058A. Apogee: 632 km (392 mi). Perigee: 433 km (269 mi). Inclination: 51.1000 deg. Period: 95.20 min. Summary: Solar radition data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1971 November 15 - . 05:52 GMT - . Launch Site: San Marco. LV Family: Scout. Launch Vehicle: Scout B. LV Configuration: Scout B S163CR.
  • Explorer 45 - . Payload: SSS A. Mass: 52 kg (114 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: SSS. Decay Date: 1992-01-10 . USAF Sat Cat: 5598 . COSPAR: 1971-096A. Apogee: 18,149 km (11,277 mi). Perigee: 272 km (169 mi). Inclination: 3.2000 deg. Period: 322.80 min. Summary: Studies magnetosphere, energetic particles. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1972 August 13 - . 15:10 GMT - . Launch Site: Wallops Island. Launch Complex: Wallops Island LA3A. LV Family: Scout. Launch Vehicle: Scout D-1. LV Configuration: Scout D-1-F S184C.
  • Explorer 46 - . Payload: Meteoroid Technology Satellite. Mass: 136 kg (299 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Earth. Type: Micrometeoroid satellite. Spacecraft: MTS. Decay Date: 1979-11-02 . USAF Sat Cat: 6142 . COSPAR: 1972-061A. Apogee: 811 km (503 mi). Perigee: 492 km (305 mi). Inclination: 37.7000 deg. Period: 97.70 min. Summary: Micrometeoroid tests. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1972 September 23 - . 01:20 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta 1604. LV Configuration: Delta 1604 579/D90.
  • Explorer 47 - . Payload: IMP H. Mass: 376 kg (828 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. USAF Sat Cat: 6197 . COSPAR: 1972-073A. Apogee: 235,600 km (146,300 mi). Perigee: 201,100 km (124,900 mi). Inclination: 17.2000 deg. Period: 17,670.00 min. Summary: Investigated cislunar radiation, Earth's magnetosphere, interplantary magnetic field. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C). .

1972 November 15 - . 22:13 GMT - . Launch Site: San Marco. LV Family: Scout. Launch Vehicle: Scout D-1. LV Configuration: Scout D-1-F S170CR.
  • Explorer 48 - . Payload: SAS B. Mass: 185 kg (407 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: SAS. Decay Date: 1976-08-20 . USAF Sat Cat: 6282 . COSPAR: 1972-091A. Apogee: 526 km (326 mi). Perigee: 526 km (326 mi). Inclination: 1.0000 deg. Period: 95.20 min. Summary: Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1973 June 10 - . 14:13 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta 1913. LV Configuration: Delta 1913 581/D95.
  • Explorer 49 - . Payload: RAE B. Mass: 328 kg (723 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: X-ray astronomy satellite. Spacecraft: RAE. USAF Sat Cat: 6686 . COSPAR: 1973-039A. Summary: Radio Astronomy Explorer; measured galactic, stellar radio noise. Lunar Orbit (Selenocentric). Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B)..

1973 October 26 - . 02:26 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta 1604. LV Configuration: Delta 1604 582/D97.
  • Explorer 50 - . Payload: IMP J. Mass: 371 kg (817 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Magnetosphere satellite. Spacecraft: IMP. USAF Sat Cat: 6893 . COSPAR: 1973-078A. Apogee: 244,361 km (151,838 mi). Perigee: 190,749 km (118,525 mi). Inclination: 31.6000 deg. Period: 17,576.70 min. Summary: Solar flare and radiation monitor. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1973 December 16 - . 06:18 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2W. LV Family: Delta. Launch Vehicle: Delta 1900. LV Configuration: Delta 1900 585/D99.
  • Explorer 51 - . Payload: AE C. Mass: 658 kg (1,450 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: AE. Decay Date: 1978-12-12 . USAF Sat Cat: 6977 . COSPAR: 1973-101A. Apogee: 4,306 km (2,675 mi). Perigee: 155 km (96 mi). Inclination: 68.1000 deg. Period: 132.50 min. Summary: Atmospheric Explorer; upper atmospheric research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1974 June 3 - . 23:09 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout E-1. LV Configuration: Scout E-1 S191C.
  • Explorer 52 - . Payload: Hawkeye. Mass: 27 kg (59 lb). Nation: USA. Agency: NASA Langley. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: Hawkeye. Decay Date: 1978-04-30 . USAF Sat Cat: 7325 . COSPAR: 1974-040A. Apogee: 125,569 km (78,024 mi). Perigee: 469 km (291 mi). Inclination: 89.0000 deg. Period: 3,032.00 min. Summary: Solar wind experiments. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1975 May 7 - . 22:45 GMT - . Launch Site: San Marco. LV Family: Scout. Launch Vehicle: Scout F. LV Configuration: Scout F-1 S194C.
  • Explorer 53 - . Payload: SAS C. Mass: 195 kg (429 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: SAS. Decay Date: 1979-04-09 . USAF Sat Cat: 7788 . COSPAR: 1975-037A. Apogee: 507 km (315 mi). Perigee: 498 km (309 mi). Inclination: 3.0000 deg. Period: 94.70 min. Summary: Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1975 October 6 - . 09:00 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2W. LV Family: Delta. Launch Vehicle: Delta 2910. LV Configuration: Delta 2910 600/D115.
  • Explorer 54 - . Payload: AE D. Mass: 676 kg (1,490 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: AE. Decay Date: 1976-03-12 . USAF Sat Cat: 8353 . COSPAR: 1975-096A. Apogee: 3,819 km (2,373 mi). Perigee: 151 km (93 mi). Inclination: 90.1000 deg. Period: 126.80 min. Summary: Atmospheric Explorer; atmospheric research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1975 November 20 - . 02:06 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta 2910. LV Configuration: Delta 2910 604/D117.
  • Explorer 55 - . Payload: AE E. Mass: 721 kg (1,589 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: AE. Decay Date: 1981-06-10 . USAF Sat Cat: 8440 . COSPAR: 1975-107A. Apogee: 3,002 km (1,865 mi). Perigee: 154 km (95 mi). Inclination: 19.7000 deg. Period: 117.70 min. Summary: Atmospheric Explorer. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B). .

1975 December 6 - . 03:35 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC5. LV Family: Scout. Launch Vehicle: Scout F. LV Configuration: Scout F-1 S196C. FAILURE: Failure. Failed Stage: U.
  • Explorer (56) - . Payload: DAD-A. Mass: 71 kg (156 lb). Nation: USA. Agency: NASA. Program: Explorer. Class: Earth. Type: Atmosphere satellite. Spacecraft: DAD. Decay Date: 1975-12-05 . COSPAR: F751206A. Summary: Dual Air Density; air density experiments..
  • DAD-B - . Payload: DAD-B. Nation: USA. Agency: AFSC. Program: Explorer. Spacecraft: DAD. COSPAR: F751206B.

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