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This spacecraft was placed into a high-inclination, highly eccentric earth orbit. The apogee point was located near the ecliptic plane and had an initial local time of about 1900 h. The spacecraft was spin-stabilized and had an initial spin period of 2.6 s. The spin vector was approximately perpendicular to the ecliptic plane. Like the earlier IMPs, this spacecraft was instrumented to study interplanetary magnetic fields, energetic particles, and plasma. The spacecraft optical aspect system failed on 04 March 1969. Otherwise, useful data were acquired until just before spacecraft reentry, which occurred on 03 May 1969.

Alternate Names

  • 02817
  • Explorer 34
  • IMP 4

Facts in Brief

Launch Date: 1967-05-24
Launch Vehicle: Delta
Launch Site: Vandenberg AFB, United States
Mass: 163 kg

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Mr. Paul ButlerProject ManagerNASA Goddard Space Flight Center
Dr. Frank B. McDonaldProject ScientistNASA Goddard Space Flight Center
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