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26.5-KHz to 3-MHz Radio Wave

NSSDCA ID: 1974-097A-06

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


This experiment (E5c) shared the 32-m, tip-to-tip, electric dipole antenna with experiments -04 and -05. A dual (redundant) 16-frequency channel radiometer, with approximately logarithmically spaced channels, was used to detect type III radio emissions associated with solar flare events in the frequency band 26.5 kHz to 3 MHz. The experiment sampling rate was synchronized such that each spacecraft revolution was divided into 32 sectors. The sequence and frequency of sampling depended on the instrument operational mode (one of four) and the spacecraft bit rate. The most rapid sampling possible for a single-frequency channel was once every 1/32 of a satellite spin period, or about .03 s. A typical sampling sequence was for one frequency channel to be sampled for 16 sectors (1/2 revolution), followed by the next. One half of the 32-m dipole failed to extend properly during deployment, and was short-circuited to the spacecraft ground. The resulting antenna configuration was that of a monopole with an operational effective length of about 8 m. This shorter configuration resulted in increased radio-frequency interference (rfI) of from 3 to 30 dB above expected levels, and a loss of 6 dB in gain. Another problem was unexpected interference with the high-gain telemetry antenna. This added 60 dB rfI at 27.5 kHz, decreasing with increasing frequency, so that above 200 kHz it produced no detectable interference. For more details about the instrument and modes of operation, see p. 250 of Raumfahrtforschung, v. 19, n. 5, 1975.

Alternate Names

  • Helios-A/26_5-KHzto3-MHzRadioWave
  • Solar Wind Plasma and Radio Wave

Funding Agency

  • NASA-Office of Space Science (United States)


  • Solar Physics: Radio

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. Richard R. WeberOther InvestigatorNASA Goddard Space Flight
Dr. Robert G. StoneOther InvestigatorNASA Goddard Space Flight
Dr. Paul J. KelloggOther InvestigatorUniversity of
Prof. Donald A. GurnettPrincipal InvestigatorUniversity of Iowa
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