NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Radio Science: Celestial Mechanics

NSSDCA ID: 1996-068A-05

Mission Name: Mars Pathfinder


The Mars Pathfinder Celestial Machanics Radio Science Experiment was used to study the orbits of Earth and Mars and the rotation of Mars through Earth-based radio tracking of the Pathfinder lander. The X-band (8 GHz) radio direct-to-Earth transmissions from the Pathfinder lander were used to obtain precise range and Doppler measurements from Earth, giving the relative position and motion of the lander on the surface of Mars. This data provides precise information on the relative orbital positions of Earth and Mars and on the rotation of Mars, in particular the secular precession of the longitude of the node, the short period nutation of the obliquity and the node, seasonal and tidal variations in the length of day and the polar motion or wobble of the figure axis and spin axis. This information will improve the accuracy of the value of the polar moment of inertia which in turn will yield information on the internal structure and composition of Mars and the possible size of the core.

Preliminary results from the experiment show that Mars may have a solid iron core with a radius of about 1300 km or more, or a mixed iron and sulfur core about 2000 km in radius.

Alternate Names

  • MarsPathfinder/RadioScience:CelestialMechanics
  • urn:nasa:pds:context:instrument:rss.mpfl


  • Planetary Science: Celestial Mechanics
  • Planetary Science: Geology and Geophysics

Additional Information

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



NameRoleOriginal AffiliationE-mail

Selected References

  • Folkner, W. M., et al., Mars dynamics from Earth-based tracking of the Mars Pathfinder lander, J. Geophys. Res., 102, No. E2, 4057-4064, doi:10.1029/96JE02125, Feb. 1997.
  • Folkner, W. M., et al., Interior structure and seasonal mass redistribution of Mars from radio tracking of Mars Pathfinder, Science, 278, No. 5344, 1749-1752, doi:10.1126/science.278.5344.1749, Dec. 1997.
[] NASA Logo -