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Orbiter Radio Science

NSSDCA ID: 1975-083A-04

Mission Name: Viking 2 Orbiter
Principal Investigator:Dr. William H. Michael, Jr.


There are four distinct sets of Viking radio science data, three using orbiter data and one primarily using lander data with calibrations from orbiter data. The orbiter tracking data, obtained from the two-way, orbiter-earth S-band and X-band radio links, consist of Doppler frequencies and time-of-flight range measurements. These determined the position and motion of the orbiters, and can be used to study the Mars gravitational field, the plasma in interplanetary space, and the structure of the solar corona when the spacecraft was on the opposite side of the sun. The occultation data were obtained from these same radio links by analog recording of the signal when a spacecraft was passing into or out of occultation with Mars. The data can be used to produce altitude profiles of the temperature, density, and pressure of the atmosphere (including the ionosphere) and to measure the radius of the planet using a large number of surface points. The surface properties aspect of this investigation utilized the UHF (381 MHz) signal on which the landers transmitted data to the orbiters. At the beginning or end of a data transmission session, when the orbiter was near the lander's horizon, the strength of the received signal was recorded as a function of time. These signal "fading patterns," resulting from interaction of the radio waves with the Martian surface, contain information about the physical properties of the surface near the landers. The lander tracking data from the two-way direct lander-earth S-band links permit determination of the location of the landers and studies of the motion of the planet.

Alternate Names

  • Viking2Orbiter/OrbiterRadioScience
  • urn:nasa:pds:context:instrument:rss.vo2


  • Planetary Science: Atmospheres
  • Planetary Science: Geology and Geophysics

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. William H. Michael, Jr.Team LeaderNASA Langley Research Center
Dr. Irwin I. ShapiroTeam MemberMassachusetts Institute of
Prof. G. Leonard TylerTeam MemberStanford
Mr. Dan L. CainTeam MemberNASA Jet Propulsion Laboratory
Dr. Mario D. GrossiTeam MemberRaytheon
Dr. Joseph P. BrenkleTeam MemberNASA Jet Propulsion Laboratory
Dr. Robert H. TolsonTeam MemberNASA Langley Research
Dr. J. G. DaviesTeam MemberUniversity of Manchester
Dr. Charles T. StelzriedTeam MemberNASA Jet Propulsion
Dr. George H. BornTeam MemberNASA Jet Propulsion
Dr. Robert D. ReasenbergTeam MemberMassachusetts Institute of
Dr. Gunnar F. LindalTeam MemberNASA Jet Propulsion Laboratory

Selected References

  • Michael, W. H., Jr., et al., Radio science experiments - The Viking Mars Orbiter and Lander, Icarus, 16, 57-73, doi:10.1016/0019-1035(72)90137-6, Feb. 1972.
  • Michael, W. H., Jr., et al., Viking Lander location and spin axis of Mars determination from radio tracking data, Science, 193, 803, doi:10.1126/science.193.4255.803, Aug. 1976.
  • Sjogren, W. L., Mars gravity - high resolution results from Viking Orbiter 2, Science, 203, No. 4384, 1006-1010, doi:10.1126/science.203.4384.1006, Mar. 1979.
  • Simpson, R. A., et al., Viking bistatic radar observations of the Hellas basin on Mars - preliminary results, Science, 203, No. 4375, 45-46, doi:10.1126/science.203.4375.45, Jan. 1979.
  • Michael, W. H., Jr., et al., The Viking radio science investigations, J. Geophys. Res., 82, No. 28, 4293-4295, doi:10.1029/JS082i028p04293, Sept. 1977.
  • Simpson, R. A., et al., Viking bistatic radar experiment: Summary of results in near-equatorial regions, J. Geophys. Res., 89, No. B12, 10385-10404, doi:10.1029/JB089iB12p10385, Nov. 1984.
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