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NEAR Radio Science (RS) and Gravimetry

NSSDCA ID: 1996-008A-05

Mission Name: NEAR Shoemaker
Principal Investigator:Dr. Donald K. Yeomans


The radio science experiment (RS) will use the NEAR telemetry system to estimate the gravity field of the asteroids 253 Mathilde and 433 Eros. The principal scientific objectives of this investigation are to determine the mass and gravity variations of the asteroids and combine this data with information from the multispectral imager and laser rangefinder to estimate the density of bodies and constrain the internal structure. Radio telemetry will also be used to determine the rotational and orbital characteristics of Eros.

The NEAR radio consists of a 3848 MHz X-band transponder. Tracking uplink is X-band at 7182 MHz and downlink is also X-band at 8438 MHz. The experiment has no listed mass or power requirements because it is part of the engineering subsystems. The experiment will measure the two-way Doppler shift in radio transmissions between the spacecraft and Earth to an accuracy of 0.1 mm/s to determine line-of-sight velocity variations in the spacecraft motion, which will be analyzed to determine the effect of the asteroid's gravity field on spacecraft acceleration. This will give a bulk estimate of the mass of Mathilde within 10% from the flyby, and of Eros to within 0.1% from orbit. For Eros, continuous tracking will yield an estimated gravity field. This information, combined with data from other NEAR instruments, will allow modelling of the bulk density and the internal density distribution of the asteroid. Tracking of the spacecraft position will give information on the orbital and rotational characteristics of Eros.

Alternate Names

  • NEARShoemaker/RS
  • RS
  • urn:nasa:pds:context:instrument:rss.near

Funding Agency

  • National Aeronautics and Space Administration (United States)


  • 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. Donald K. YeomansTeam LeaderNASA Jet Propulsion Laboratory
Dr. Jean-Pierre BarriotTeam MemberCentre National d'Etudes
Dr. Alexander S. KonoplivTeam MemberNASA Jet Propulsion

Selected References

  • Yeomans, D. K., et al., The NEAR Radio Science investigations, J. Geophys. Res., 102, No. E10, 23775-23780, doi:10.1029/96JE02708, Oct. 1996.
  • Yeomans, D. K., et al., Estimating the mass of asteroid 253 Mathilde from tracking data during the NEAR flyby, Science, 278, No. 5346, 2106-2109, doi:10.1126/science.278.5346.2106, Dec. 1997.
  • Bokulic, R. S., and W. V. Moore, Near Earth Asteroid Rendezvous (NEAR) spacecraft Solar Conjunction Experiment, J. Spacecr. Rocket, 36, No. 1, 87-91, doi:10.2514/2.3418, Jan.-Feb. 1999.
  • Miller, J. K., et al., Determination of shape, gravity, and rotational state of asteroid 433 Eros, Icarus, 155, No. 1, 3-17, Jan. 2002.
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