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Electric Field Experiment (EFE)

NSSDCA ID: 1992-064A-01

Mission Name: Freja
Principal Investigator:Dr. Goran T. Marklund


The experiment was made using three pairs of spherical probes of diameter 6 cm, mounted on the spin plane; two of these pairs were 30 meters apart, and the third 20 meters apart, tip to tip. Assigning labels 1 through 6 to the probes, the following potentials were sampled during the 'normal mode": V12, V34, V56, V1, V2, V3, V4, and the spacecraft potential Vfg; for onboard storing times, V56, and Vfg were omitted. The spatial resolution of the probe voltages was varied between 1 meter (burst mode) and 10 meters (normal mode). When operated on a "compressed mode" the spatial resolution was 40 meters. The burst mode could be activated either by ground command or by an automatic inhouse trigger; there were also instances when all instuments were commanded to be simultaneously on burst mode. As needed, one of the probes was used at times as a Langmuir probe to measure plasma density and temperature, by a sweeping current of -900 nA to +900 nA. The data was acquired at 768, 1536, and 6144 samples per second. The instrument remains operational as of 11 July 96.

Alternate Names

  • EFE
  • Freja/EFE

Facts in Brief

Mass: 4.871 kg
Power (avg): 9.4 W
Bit rate (avg): 30.72 kbps

Funding Agencies

  • Max-Planck-Institut (Germany)
  • Unknown (Sweden)


  • Space Physics: Ionospheric Studies
  • Space Physics: Magnetospheric Studies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Arne PedersenCo-InvestigatorESA-European Space Research and Technology
Prof. Forrest S. MozerCo-InvestigatorUniversity of California,
Prof. Carle-Gunne FalthammarCo-InvestigatorRoyal Institute of
Dr. Gerhard HaerendelCo-InvestigatorMax-Planck-Institut fur Extraterrestrische
Prof. Pekka J. TanskanenCo-InvestigatorUniversity of
Dr. Lars G. BlombergCo-InvestigatorRoyal Institute of
Dr. Goran T. MarklundPrincipal InvestigatorRoyal Institute of
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