NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

20-s CPME + EPE Particle, 15-s Magnetic Field and 1-min Plasma Merged Data Set


Availability: At NSSDC, Ready for Electronic Access

Time span: 1973-10-28 to 2000-12-31


This is a composite data set (the "IMP merge data set") which captures high resolution data from the IMP-8 Charged Particle Monitoring Experiment (CPME; PI is Decker), Energetic Particle Experiment (EPE; PI is Williams), Magnetometer (current PI is Lepping), and MIT Plasma Experiment (current PI is Lazarus). Most CPME rates are included at 20.48 sec resolution; electron rates, and low energy proton rates, are included at 10.24 sec resolution. Longitudinally sectored rates for .29-.50 MeV electrons are given at 10.24 sec resolution, and 20.48-s sectored rates for some alpha and medium-Z nuclei channels are also given. EPE data included are 20.48-s, 22.5-deg resolution rates for .05-.22 and .22-.80 MeV protons, .03-.10 and .10-.20 MeV electrons, and for one channel responding to "all species above 15 keV." Magnetometer data include 20.48-s averages of the field vector in GSE and GSM coordinates, as well as the 15.36-s averages contributing to each 20.48-s average. Plasma parameters include density, temperature, and flow speed and direction; these parameters are at 1-2 min resolution, but have been assigned to the 20.48-s records as appropriate. The CPME data and EPE data constitute about 60% and 20% of the totality of 425 words per 20.48-s logical records. Additional parameters include time, spacecraft position and velocity vectors, positions of sun (GEI coordinates) and moon (GSE), and kp, AE, C9, Dst, and sunspot indices. In 1997, a new version of this data set was created at APL on CD-Recordable disks (5 CD's per year) which corrected a time tagging problem associated with magnetometer data and which extended the time coverage. The composite data set was created at JHU/APL, with key roles played by Pat Briggs, Tom Armstrong, Rob Decker, Jack Gunther, and others. The data set was initially created (early 1990's) on VAX binary tapes, with about 20 days of data per full tape. The data are now available in annual, g-zipped ASCII files at merge_20s_ascii/

Alternate Names

  • 20-s Prtcl, 15-s Mag, 1-m Plsma


  • Space Physics: Magnetospheric Studies
  • Space Physics: Heliospheric Studies


  • 73-078A-01K
  • 73-078A-02K
  • 73-078A-05F
  • 73-078A-08J

Additional Information



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



NameRoleOriginal AffiliationE-mail
Mr. Jack L. GuntherData ProviderApplied Physics
[] NASA Logo -