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Atmospheric Propagation (MPRO)

NSSDCA ID: 1978-078G-07

Mission Name: Pioneer Venus Small Probe (Day)
Principal Investigator:Dr. Thomas A. Croft


This experiment used the Deep Space Network (DSN) telemetry data. The objectives were (1) to determine the atmospheric structure of Venus as it affects the intensity and refraction of Probe telemetry signals, and (2) to investigate the interference between the direct ray and a surface-reflected component as a means of assessing communications reliability for the design of future probe missions.

The radio signals transmitted to Earth from the four probes (S-band, 2291 to 2293 MHz, approximately 13 cm wavelength, depending on the probe) had a broad beam-width, resulting in a small downward component. Some of this component scattered off the surface of Venus, returned through the atmosphere, and was detected at Earth. The S-band antennas were mounted on top of the probes, but because the probe zenith to Earth angle ranged from 53 to 61 degrees, the signals did not go directly down to scatter to Earth. Comparison between the direct radio signals and the scattered signals from the surface gave information on the refraction of the signal in the atmosphere, Venus atmospheric winds, and surface parameters.

Alternate Names

  • MPRO
  • PioneerVenusSmallProbeDay/MPRO


  • Planetary Science: Atmospheres

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Thomas A. CroftPrincipal InvestigatorSRI

Selected References

  • Colin, L., Ed., and D. M., Ed. Hunten, Pioneer Venus experiment descriptions, Space Sci. Rev., 20, No. 4, 451-525, doi:10.1007/BF02186463, June 1977.
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