Explorer 33

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Explorer 33
Mission type Magnetospheric research
Operator NASA
COSPAR ID 1966-058A
SATCAT no. 2258
Mission duration 1,876 days (5 years, 1 month and 21 days)
Spacecraft properties
Manufacturer Goddard Space Flight Center
Launch mass 212.0 kilograms (467.4 lb)
Start of mission
Launch date July 1, 1966, 16:02:25 (1966-07-01UTC16:02:25Z) UTC
Rocket Delta E1
Launch site Cape Canaveral LC-17A
End of mission
Last contact September 21, 1971 (1971-09-22)
Orbital parameters
Reference system Geocentric
Regime HEO
Eccentricity 0.2832989990711212
Perigee 265,689 kilometers (165,091 mi)
Apogee 480,762 kilometers (298,732 mi)
Inclination 24.399999618530273°
Period 38792.0 minutes
RAAN 173.5399 degrees
Argument of perigee 119.2000 degrees
Mean anomaly 21.7899 degrees
Mean motion 0.03712071
Epoch 12 May 1971 12:00:00
Revolution no. 142

Explorer 33 (also known as AIMP-D or IMP-D) was a spacecraft in the Explorer program launched by NASA on July 1, 1966 on a mission of scientific exploration.


Originally intended for a lunar orbit, mission controllers worried that the spacecraft's trajectory was too fast to guarantee lunar capture.[1] Consequently, mission managers opted for a backup plan of placing the craft into an eccentric Earth orbit with a perigee of 265,679 km and an apogee of 480,762 km — still reaching distances beyond the Moon's orbit.[2]

Despite not attaining the intended lunar orbit, the mission met many of its original goals in exploring solar wind, interplanetary plasma, and solar X-rays.[3] Principal investigator James Van Allen used electron and proton detectors aboard the spacecraft to investigate charged particle and X-ray activity.[4] Astrophysicists N. U. Crooker, Joan Feynman, and J. T. Gosling used data from Explorer 33 to establish relationships between the Earth's magnetic field and the solar wind speed near Earth.[5]

See also[edit]


  1. ^ J. J. Madden (December 1966). "Interim Flight Report, Anchored Interplanetary Monitoring Platform, AIMP I - Explorer XXXIII" (PDF). NASA Goddard Space Flight Center. 
  2. ^ "IMP Chronology". Encyclopedia Astronautica. 
  3. ^ "Explorer 33 (NSSDC ID: 1966-058A)". NASA / National Space Science Data Center. 2008-04-02. Retrieved 2008-07-04. 
  4. ^ "Explorer 33 – Electron and Proton Detectors". NASA / National Space Science Data Center. 2008-04-02. Retrieved 2008-07-04. 
  5. ^ Crooker, N. U.; Feynman, J.; Gosling, J. T. (1977-05-01). "On the high correlation between long-term averages of solar wind speed and geomagnetic activity". NASA. Retrieved 2008-07-04. 

External links[edit]