IMP-8 CPME and EPE Background Information

  1. IMP-8 Satellite
  2. The IMP-8 satellite is the last in a family of ten Interplanetary Monitoring Platforms (see the IMP-8 Project Information Web site at NASA/GSFC). IMP-8 was launched on 26 October 1973 into a nearly circular orbit about the Earth at a radius ~35 Earth radii. It spends 60+% of each 12-day orbit in the solar wind, with the rest of the time in the magnetosheath and magnetosphere. IMP-8 is a spin-stabilized spacecraft, with its spin vector nearly perpendicular to the ecliptic plane, and a spin rate of 24 rpm.

  3. CPME and EPE Instruments
  4. The Charged Particle Measurements Experiment (CPME) and the Energetic Particle Experiment (EPE ) on IMP-8 have been operating successfully for 27 years and have generated a wealth of high-quality data that have led to new discoveries and have resulted in hundreds of publications. Both instruments continue to perform without problems.

    The combined CPME-EPE data sets have been used to address a wide variety of scientific problems. These include studies of energetic particle activity in and around Earth's magnetosphere, solar energetic particle events, solar X-rays, shock accelerated ions and electrons in the interplanetary medium and near Earth's bow shock, iron group ions in high speed solar wind streams, the intensity gradients of galactic cosmic rays, and dynamical chaos in the magnetosphere. This rich and varied scientific output has resulted from the efforts of several groups, including those at the Applied Physics Laboratory, University of Kansas, University of Calgary, Canada, at the Demokritos University of Thrace in Greece.

    The CPME measurements have been used to generate hourly averages of particle intensities published for over more than a decade in Solar Geophysical Data. These data have been used by the at-large science community for many correlative studies in a variety of scientific problems. In addition, a complete set of hourly averages of energetic particle activity at energies >1, 2, 4, 10, 30, and 60 MeV starting from launch of IMP-7 (day 275, 1972) have been delivered both on tape and in graphical output to the National Space Science Data Center (NSSDC) for use by the science community in potential correlative investigations. This body of data represents the only one of its kind, to our knowledge, and is now extending into its third consecutive solar activity cycle.

  5. CPME and EPE Data Processing
  6. Processing of IMP-8 CPME and EPE data at JHU/APL is summarized in the PDF document IMP_Data_Processing_Summary (140K).

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