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Injun 5



Injun 5 (Explorer 40) was a 71-kg magnetically oriented spacecraft and was launched by a Scout rocket, together with a 3.65-m inflatable balloon (Explorer 39) used for air density measurements. Injun 5 was designed to accomplish the following objectives: (1) comprehensive study of the downward flux of charged particles, (2) study of very low frequency (VLF) radio emission in the ionosphere associated with the downward flux, (3) study of geomagnetically trapped protons, alpha particles, and electrons, (4) observation of solar cosmic rays, (5) observation of the continuing decay of the Starfish artificial radiation belt, and (6) study of the temperature and density of electrons and positive ions of thermal and near thermal energy. The spacecraft systems performed normally except for the malfunction of the solar cell power dump device (shortly after launch) which caused the solar cells to deliver a lower power level to the experiments and reduced the time during which the onboard tape recorder could be run. The passive magnetic alignment became effective in mid-December 1968. The spacecraft was turned off from May 31, 1970, to February 18, 1971, after this period it was turned on again. The spacecraft was put in an operational off-mode in early June 1971, and became inoperable shortly thereafter.

Image courtesy of the University of Iowa

Alternate Names

  • 03338
  • Explorer 40
  • Injun IE-C
  • Injun-C
  • Injun5

Facts in Brief

Launch Date: 1968-08-08
Launch Vehicle: Scout
Launch Site: Vandenberg AFB, United States
Mass: 71.4 kg

Funding Agencies

  • NASA-Office of Space Science Applications (United States)
  • Department of Defense-Department of the Navy (United States)


  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. H. Kent Hills



NameRoleOriginal AffiliationE-mail
Mr. Robert L. BrechwaldGeneral ContactUniversity of
Mr. John E. RogersProject ManagerUniversity of Iowa
Diagram of Injun 5

Injun 5 Diagram

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