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Wave and Plasma Analyzer (APV-V)

NSSDCA ID: 1984-125A-11

Mission Name: Vega 1
Principal Investigators:Dr. Rejean J. L. Grard
Principal Investigators:Dr. Christian Beghin


The primary objectives of this investigation (APV-V, or Epinoche, or Langmuir Probes and High Frequency Wave Analyzer) were (1) to measure the density of the solar wind just before it is influenced by cometary constituents, thereby establishing a reference for understanding the subsequent solar wind-comet interaction, (2) to observe the mass loading of the solar wind by cometary ions either directly or through the associated wave instabilities, (3) to obtain plasma density and temperature profiles, as well as wave frequency spectra during the cometary transit, (4) to search for the signatures of collision-free shocks and contact surfaces, and (5) to monitor the electric potential of the spacecraft during the flyby of the nucleus. The experimental equipment consisted of an electronics box (1400 g) and two booms mounted on the outer solar panels, which carry the sensors (2 x 800 g). Power consumption was 2 W and the maximum data transmission rate was 0.48 kbs. Electric fields were measured in the frequency range 0 to 300 kHz; the low frequency fluctuations were transmitted after direct sampling of the waveform; and the upper part of the spectrum, from 8 Hz to 300 kHz, was analyzed with a set of 16 adjacent and logarithmically spaced filters. The dynamic range of the electric field measurements was about 70 dB. The plasma density and temperature were measured with two Langmuir probes. The polarization voltage of one probe was kept at a fixed value of 5 V and the low frequency fluctuations of the electron current were analyzed in the frequency range 0 to 4 Hz by direct sampling of the waveform. The potential of the second probe was swept by a sinusoidal voltage with a period of 32 s superimposed on a dc voltage; the duration of the sweep, its amplitude and its average level could be modified by telecommand. The range of the density measurements was typically 10 to 1E4 per cc for a nominal electron mean kinetic energy of 1 eV. It was foreseen, however, that the effect of plasma emission from the spacecraft surface by impact of gas and dust would have to be carefully evaluated when interpreting the plasma measurements.

Alternate Names

  • APV-V
  • Vega1/APV-V

Facts in Brief

Mass: 3 kg
Power (avg): 2 W
Bit rate (avg): 0.512 kbps


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

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Arne PedersenCo-InvestigatorESA-European Space Research and Technology
Dr. Karl KnottCo-InvestigatorESA-European Space Research and Technology Centre
Dr. Vittorio FormisanoCo-InvestigatorCNR, Space Plasma
Dr. O. A. MolchanovCo-InvestigatorIZMIRAN
Dr. Y. MichailovCo-InvestigatorIZMIRAN
Dr. M. MoguilevskiCo-InvestigatorIZMIRAN
Dr. Rejean J. L. GrardPrincipal InvestigatorESA-European Space Research and Technology
Dr. Christian BeghinPrincipal InvestigatorCNRS, Centre Spectrometric Nucleaire et

Selected References

  • Grard, R., Comet Halley's interaction with the Sun: The plasma and wave experiment on-board the Vega spacecraft, ESA Bull., No. 44, 40-43, Nov. 1985.
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