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Solar Wind Plasma Wave

NSSDCA ID: 1974-097A-04

Mission Name: Helios-A
Principal Investigator:Prof. Donald A. Gurnett


This experiment (E5a) shared the 32-m, tip-to-tip electric antenna with experiments -05 and -06. The instrument consisted of a 16-channel spectrum analyzer with approximately logarithmically equispaced center frequencies, 16 log compressors, 16 RC integrators for averaging the log compressed electric field amplitude between readouts, and 16 peak detectors which were reset after readout. The 16 averages and 16 peak log values were sampled almost simultaneously. The channels covered the frequency range of about 20 Hz to 200 kHz, with four channels per decade of frequency. The log compressors had a dynamic range of 100 dB. Sampling rate depended in detail on the spacecraft bit rate and telemetry format. The fastest real-time telemetered rate was for 16 averages and 16 peak values to be sampled every 1.125 s. Whenever a very strong signal was detected in a pre-selected channel, the shock alarm data mode was initiated in which the electric field spectrum, magnetic field, and plasma data were recorded into spacecraft memory for a period starting before and terminating after the triggering signal time. The maximum sampling rate of the spectrum data in this mode was 14.2 samples per second for each channel. One half of the dipole antenna failed to extend properly and was short-circuited to the spacecraft ground. The resultant configuration was that of a monopole which was calculated to have an effective length of approximately 8 m. The primary detrimental effects were the loss of 6 dB in E-field sensitivity due to the shortened antenna and the increase in the 178 kHz channel by 25 dB. Solar cell and sheath effects caused interference in the lowest 6 channels (which was less severe with increasing channel frequency). For more details, see J. Geophys. Res., v. 82, p. 632, 1975, and pp. 245-247 of Raumfahrtforschung, v. 19, n. 5, 1975.

Alternate Names

  • Helios-A/SolarWindPlasmaWave
  • Solar Wind Plasma and Radio Wave

Funding Agency

  • NASA-Office of Space Science (United States)


  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Dr. H. Kent Hills



NameRoleOriginal AffiliationE-mail
Dr. Robert G. StoneOther InvestigatorNASA Goddard Space Flight
Dr. Paul J. KelloggOther InvestigatorUniversity of
Dr. Siegfried J. BauerOther InvestigatorUniversitat Graz, Austria
Prof. Donald A. GurnettPrincipal InvestigatorUniversity of Iowa
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