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Sweep-Frequency Sounder

NSSDCA ID: 1962-049A-01

Mission Name: Alouette 1
Principal Investigators:Mr. Donald B. Muldrew
Principal Investigators:Dr. Eldon S. Warren


The purpose of the sweep frequency sounder was to conduct synoptic measurements of the electron density distribution in the ionosphere at altitudes between 300 and 1000 km. The instrumentation consisted of a radio transmitter/receiver that recorded the time delay between a transmitted and returned radio pulse. A continuum of frequencies between 0.5 and 12 MHz was sampled once every 18 s. Several delay times were usually observed for each frequency due to ground reflections, plasma resonances, birefringence of the ionosphere, nonvertical propagation, etc. Delay time was primarily a function of distance traversed by the signal, the electron density along the propagation path, and the mode of propagation. The standard data form was an ionogram (graph) showing time (virtual distance of signal reflection from the satellite) vs radio frequency. Two other common forms of data were prepared from the ionograms. They were (1) digital frequency data and/or virtual height values of characteristic ionospheric features and (2) computations of electron density profiles. Performance far exceeded expectations for the experiment. Initially, observations were recorded for about 6 h per day. The experiment provided data for 10 full years.

Alternate Names

  • Alouette1/Sweep-FrequencySounder
  • Sweep Frequency Sounder

Funding Agency

  • Defence Research Board-Defence Research Telecommunications Establishme (Canada)


  • Space Physics: Ionospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Mr. Robert W. KnechtOther InvestigatorNational Bureau of Standards
Mr. John E. JacksonOther InvestigatorNASA Goddard Space Flight Center
Dr. Lawrence ColinOther InvestigatorNASA Ames Research Center
Dr. George Leroy NelmsOther InvestigatorDepartment of Communications/Communications Research Centre
Dr. J. H. WhittekerOther InvestigatorDepartment of Communications/Communications Research Centre
Dr. Joseph W. KingOther InvestigatorRutherford Appleton Laboratory
Dr. Eldon S. WarrenPrincipal InvestigatorDepartment of Communications/Communications Research Centre
Mr. Donald B. MuldrewPrincipal InvestigatorDepartment of Communications/Communications Research
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