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IMP-8 / Explorer 50
Credit - NASA

Other Designations: Interplanetary Monitoring Platform. Class: Earth. Type: Magnetosphere. Destination: High Earth Orbit. Nation: USA. Agency: NASA. Manufacturer: NASA Greenbelt.

The IMP series were managed by the Goddard Space Flight Center with the primary objectives of investigation of interplanetary plasma and the interplanetary magnetic field. The orbiting of IMP satellites in a variety of interplanetary and earth orbits allowed study of spatial and temporal relationships of geophysical and interplanetary phenomena simultaneously by several other National Aeronautics and Space Administration satellites. The IMP network provided a crucial 'early warning network' of solar flare activity for Apollo manned missions that ventured beyond the Van Allen Radiation Belts.

Typical orbit: 56731 x 230661 km, 40.9 deg inclinaton.

IMP Chronology

1963 November 27 - Explorer 18 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17B. Launch Vehicle: Delta. Mass: 62 kg (136 lb). Perigee: 192 km (119 mi). Apogee: 197,616 km (122,792 mi). Inclination: 33.30 deg. Period: 5,666.20 min.
Radiation data; Interplanetary Monitoring Program. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1964 October 4 - Explorer 21 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17A. Launch Vehicle: Delta. Mass: 62 kg (136 lb). Perigee: 191 km (118 mi). Apogee: 95,590 km (59,390 mi). Inclination: 33.50 deg. Period: 2,097.00 min.
Lower than planned orbit. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1965 May 4 - Three-station Apollo Solar Particle Alert Network ordered - Program: Apollo.
NASA Associate Administrator for Manned Space Flight George E. Mueller concurred with a plan of MSC Director Robert R. Gilruth to implement a three-station developmental Solar Particle Alert Network. Mueller said he understood that Gilruth would "review the necessity for the Guaymas station, and that you will examine having all data reduction related to this network carried out under contract," and adding that he felt the program would be enhanced if arrangement could be made to involve one or more academic institutions in the analysis of data.

1965 May 29 - Explorer 28 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17B. Launch Vehicle: Delta. Mass: 58 kg (127 lb). Perigee: 229 km (142 mi). Apogee: 261,206 km (162,305 mi). Inclination: 30.50 deg. Period: 8,419.70 min.
Magnetic field, radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1966 July 1 - Explorer 33 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17A. Launch Vehicle: Delta. Mass: 93 kg (205 lb). Perigee: 265,679 km (165,084 mi). Apogee: 480,762 km (298,731 mi). Inclination: 24.10 deg. Period: 38,792.40 min.
Intended to enter lunar orbit. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1967 May 24 - Explorer 34 - Program: Explorer. Launch Site: Vandenberg. Launch Complex: SLC2E. Launch Vehicle: Delta. Mass: 75 kg (165 lb). Perigee: 242 km (150 mi). Apogee: 214,379 km (133,208 mi). Inclination: 67.10 deg. Period: 6,358.20 min.
Radiation, magnetic field data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1967 July 19 - Explorer 35 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17B. Launch Vehicle: Delta. Mass: 104 kg (229 lb). Perigee: 484 km (300 mi). Apogee: 675 km (419 mi). Inclination: 32.40 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.

1969 June 21 - Explorer 41 - Program: Explorer. Launch Site: Vandenberg. Launch Complex: SLC2W. Launch Vehicle: Delta. Mass: 174 kg (383 lb). Perigee: 80,374 km (49,941 mi). Apogee: 98,159 km (60,993 mi). Inclination: 86.00 deg. Period: 4,906.30 min.
Cislunar radiation data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1971 March 13 - Explorer 43 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17A. Launch Vehicle: Delta. Mass: 288 kg (634 lb). Perigee: 1,845 km (1,146 mi). Apogee: 203,130 km (126,210 mi). Inclination: 31.20 deg. Period: 5,957.90 min.
Earth magnetosphere research. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

1972 September 23 - Explorer 47 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17B. Launch Vehicle: Delta. Mass: 376 kg (828 lb). Perigee: 201,100 km (124,900 mi). Apogee: 235,600 km (146,300 mi). Inclination: 17.20 deg. Period: 17,670.00 min.
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).

1973 October 26 - Explorer 50 - Program: Explorer. Launch Site: Cape Canaveral. Launch Complex: LC17B. Launch Vehicle: Delta. Mass: 371 kg (817 lb). Perigee: 190,749 km (118,525 mi). Apogee: 244,361 km (151,838 mi). Inclination: 31.60 deg. Period: 17,576.70 min.
Solar flare and radiation monitor. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

Bibliography:

McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: http://www.planet4589.org/jsr.html.
JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: http://msl.jpl.nasa.gov/home.html.
Ertel , Ivan D; Morse , Mary Louise; et al, The Apollo Spacecraft Chronology Vol I - IV NASA SP-4009, NASA, 1966-1974. Web Address when accessed: http://www.hq.nasa.gov/office/pao/History/SP-4009/cover.htm.
McDowell, Jonathan, Launch Log, October 1998. Web Address when accessed: http://hea-www.harvard.edu/~jcm/space/log/launch.html.
Aerospace Yearbook, 1966,
NASA Report, Experiments on Explorer XV, Project SERB, Study on the Enhanced Radiation Belts Final Report, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650024800_1965024800.pdf.
NASA Report, Interplanetary Monitoring Platform, IMP I- Explorer XVIII Second Interim Status Report, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650022993_1965022993.pdf.
NASA Report, Interplanetary Monitoring Platform IMP II- Explorer XXI Flight Report, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650022994_1965022994.pdf.
NASA Report, Observations of The Solar Wind During The Flight of Imp-I (Explorer Xviii), Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660017919_1966017919.pdf.
NASA Report, Instrumentation of the Ionosphere Direct- Measurements Satellite Explorer VIII, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19620001147_1962001147.pdf.
NASA Report, Flight report - Interplanetary Monitoring Platform IMP-II /Explorer XXI/, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660017262_1966017262.pdf.
NASA Report, Explorer 35 Attitude Control System, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690017890_1969017890.pdf.
NASA Report, Flight report - Interplanetary Monitoring Platform - IMP-I - Explorer XVIII, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660012411_1966012411.pdf.
NASA Report, Clean-Room Facilities for Explorer 35 Spacecraft, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680018839_1968018839.pdf.
NASA Report, Some results from the IMP-1 GM cosmic ray detector, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660022480_1966022480.pdf.
NASA Report, Interplanetary monitoring platform IMP III - Explorer XXVIII Interim flight report no. 2, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660028121_1966028121.pdf.
NASA Report, Performance Parameter Measurements on the Interplanetary Monitoring Platform IMP I, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660082531_1966082531.pdf.
NASA Report, AIMP /IMP-D/ technical summary description, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670017263_1967017263.pdf.
NASA Report, Interim flight report, Anchored Interplanetary Monitoring Platform AIMP I - Explorer XXXIII, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670009370_1967009370.pdf.
NASA Report, The decline and fall of IMP 3 Preliminary report, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670029727_1967029727.pdf.

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IMP-A
Credit- NASA