NASA’s IMP 8 Spacecraft

  • K. I. Paularena
  • J. H. King
Part of the NATO Science Series book series (ASIC, volume 537)


The IMP 8 spacecraft was launched by NASA on October 26, 1973, designed to perform observations in the solar wind and magnetotail. Although the average radius of the orbit is approximately 35 R E , the apogee and perigee distances over the entire mission were variable and had extreme values of 45 and 22 R E , respectively. Variations in the inclination of the orbit (0 to 55 degrees) mean that over long periods a large spread of space in the near-Earth environment is covered. About 7 to 8 days of each 12.5-day orbit are spent in the solar wind, after which the spacecraft crosses into the magnetosheath (approximately 1-3 days per orbit) and into the near-Earth magnetotail.

The suite of instruments contained on the spacecraft, of which most are still operable and funded, consists of three plasma experiments, a magnetometer, and several energetic particle experiments. Most of the data from these experiments is available either at the NSSDC or via links from the IMP 8 project web page (

With its long lifetime and near-Earth location, IMP 8 continues to provide valuable data for solar wind, magnetospheric, and cosmic ray studies. IMP’s periodic magnetosheath and magnetotail residence intervals, especially with the advent of such newer solar wind measuring spacecraft as WIND and ACE, allow for coincident studies in the magnetosheath and magnetosphere with such spacecraft as the two INTERBALLs and GEOTAIL. IMP 8 also acts as an important 1 AU baseline for studies of the outer heliosphere and for nonecliptic spacecraft such as Ulysses.


Solar Wind Solar Cycle Solar Wind Plasma Geocentric Distance Tracking Coverage 
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Copyright information

© Springer Science+Business Media Dordrecht 1999

Authors and Affiliations

  • K. I. Paularena
    • 1
  • J. H. King
    • 2
  1. 1.Center for Space ResearchMassachusetts Institute of TechnologyCambridgeUSA
  2. 2.Goddard Space Flight CenterGreenbeltUSA

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