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Scanning Electrostatic Analyzer and Electron Spectrometer

NSSDC ID: 1973-085A-03
Mission Name: Mariner 10
Principal Investigator: Prof. Herbert S. Bridge


This plasma experiment was designed to: (1) determine the mode of interaction between the planet Mercury and the solar wind; (2) make a comprehensive study of the plasma regime at Mercury; (3) verify and extend previous observations of the solar wind interaction with Venus; (4) clarify the role of electrons in the interactions; and, (5) study the solar wind between 0.4--1.0 AU. Instrumentation for the experiment consisted of two sunward-facing electrostatic analyzers (SESA) and one backward facing electron spectrometer (BESA). These three detectors were mounted on a scanning platform, which could be swept at 1 degree/s through an arc of 120 degrees centered on a direction in the ecliptic plane 6 degrees east of the spacecraft-sun line. Both SESAs failed to return data. They were to measure positive ions from 0.08--8 keV and electrons from 4--400 eV. The BESA had a fan-shaped field of view of +/-3.5 x +/-13.5 degrees. The larger angle was normal to, and symmetric about, the scan arc. An electron spectrum was obtained every 6 s, and consisted of flux measurements in fifteen logarithmically spaced energy channels (with channel width delta-E/E=6.6%) within the energy range 13.4--690 eV. Because solar wind flow past a spacecraft introduces angular distortion of the electron distribution function compared to what would be observed in the solar wind rest frame, it was possible, by taking into account this distortion and the spacecraft sheath characteristics, to derive some of the solar wind plasma parameters such as ion bulk speed, electron temperature, and electron density. The reliability of these parameters is necessarily dependent on the validity of the spacecraft sheath model employed in the analysis, and is thus affected by time changes in the ambient solar wind.

Facts in Brief

Mass: 9.7 kg
Power (avg): 6.8 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
Dr. Alan J. LazarusCo-InvestigatorMassachusetts Institute of Technology 
Dr. Samuel J. BameCo-InvestigatorLos Alamos National
Dr. Arthur J. HundhausenCo-InvestigatorNational Center for Atmospheric Research 
Dr. Leonard F. BurlagaCo-InvestigatorNASA Goddard Space Flight
Dr. S. OlbertCo-InvestigatorMassachusetts Institute of Technology 
Prof. George L. SiscoeCo-InvestigatorUniversity of California, Los
Prof. Herbert S. BridgeGeneral ContactMassachusetts Institute of Technology 
Dr. Joseph H. BinsackCo-InvestigatorMassachusetts Institute of
Dr. Conway W. SnyderCo-InvestigatorNASA Jet Propulsion Laboratory 
Dr. John R. AsbridgeCo-InvestigatorLos Alamos National
Dr. Clayne M. YeatesCo-InvestigatorNASA Jet Propulsion Laboratory 
Dr. Keith W. OgilvieCo-InvestigatorNASA Goddard Space Flight
Dr. Richard E. HartleCo-InvestigatorNASA Goddard Space Flight
Dr. Michael D. MontgomeryCo-InvestigatorLos Alamos National Laboratory 

Selected References

Ogilvie, K. W., et al., Observations at the planet Mercury by the plasma electron experiment: Mariner 10, J. Geophys. Res., 82, No. 13, 1807-1824, May 1977.

Ogilvie, K. W., et al., Observations at Mercury encounter by the plasma science experiment on Mariner 10, Science, 185, No. 4146, 145-151, July 1974.

Bridge, H. S., et al., Observations at Venus encounter by the plasma science experiment on Mariner 10, Science, 183, No. 4131, 1293-1296, Mar. 1974.

Image of the Scanning Electrostatic Analyzer and Electron Spectrometer experiment

Scanning Electrostatic Analyzer and Electron Spectrometer

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