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Energetic Particles Experiment

NSSDC ID: 1973-085A-07
Mission Name: Mariner 10
Principal Investigator: Dr. John A. Simpson


This experiment was designed to measure energetic electrons, protons, and alpha particles in the interplanetary medium and in the vicinities of Venus and Mercury. The instrumentation consisted of a main telescope and a low-energy telescope. The main telescope consisted of six co-linear sensors (five silicon detectors and one CsI scintillator) surrounded by a plastic scintillator anti-coincidence cup. One pulse height analysis was performed every 0.33 s, and counts accumulated in each coincidence/anti-coincidence mode were measured every 0.6 s. Particles stopping in the first sensor were protons and alpha particles in the range 0.62--10.3 MeV/nucleon and electrons above ~170 keV. The aperture half angle for this mode was 47 degrees, and the geometric factors were 14 sq cm-sr for electrons and 7.4 sq cm-sr for protons and alpha particles. The telescope aperture half-angle decreased to 32 degrees for coincident counts in the first and third sensors. The low-energy telescope, a two-element (plus anti-coincidence) detector with a 38 degree half angle aperture and a 0.49 sq cm sr geometrical factor, was designed to measure 0.53--1.9 MeV and 1.9--8.9 MeV protons without responding to electrons over a wide range of electron energies and intensities.

Facts in Brief

Mass: 3.8 kg
Power (avg): 1.6 W

Funding Agency

  • NASA-Office of Space Science (United States)


  • Planetary Science: Fields and Particles
  • Space Physics: Heliospheric Studies

Additional Information

Questions or comments about this experiment can be directed to: Dr. David R. Williams.



NameRoleOriginal AffiliationE-mail
Mr. James E. LamportCo-InvestigatorUniversity of Chicago 
Dr. John A. SimpsonGeneral ContactUniversity of Chicago 

Selected References

Simpson, J. A., et al., Search by Mariner 10 for electrons and protons accelerated in association with Venus, Science, 183, No. 4131, 1318-1321, Mar. 1974.

Armstrong, T. P., et al., A reinterpretation of the reported energetic particle fluxes in the vicinity of Mercury, J. Geophys. Res., 80, No. 28, 4015-4017, Oct. 1975.

Simpson, J. A., et al., Electrons and protons accelerated in Mercury's magnetic field, Science, 185, No. 4146, 160-166, July 1974.

Simpson, J. A., Reply to ``Reinterpretation of the reported energetic particle fluxes in the vicinity of Mercury'', J. Geophys. Res., 80, No. 28, 4018, Oct. 1975.

Christon, S. P., et al., Electron calibration of instrumentation for low energy, high intensity particle measurements at Mercury, J. Geophys. Res., 84, No. A8, 4277-4288, Aug. 1979.

Armstrong, T. P., et al., Comment on ``Electron calibration of instrumentation for low-energy high intensity particles measurements at Mercury'' by Christon, Daly, Eraker, Perkins, Simpson, and Tuzzolino, J. Geophys. Res., 84, No. A8, 4468-4470, Aug. 1979.

Eraker, J. H., and J. A. Simpson, Acceleration of charged particles in Mercury's magnetosphere, J. Geophys. Res., 91, No. A9, 9973-9993, Sept. 1986.

Image of the Energetic Particles Experiment experiment

Energetic Particles Experiment

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