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Radio Science

NSSDCA ID: 2007-043A-05

Mission Name: Dawn
Principal Investigator:Dr. Alexander S. Konopliv


The radio science experiment on Dawn will use the communications system, in concert with the optical imaging system, to accurately track the spacecraft motions as it orbits the asteroids and use these motions to map the gravity field. The objectives of the radio science gravity experiment are to determine the masses, global gravity fields to the 12th harmonic degree and order, the principal axes, the rotational axis, and the moments of inertia of Ceres and Vesta. This information will help estimate the bulk density, crustal and mantle density variations, and any wobble in rotation, and constrain the maximum size of an iron core if one exists, on both asteroids.

The different orbital configurations about the asteroids will yield different information about the gravity field. The initial, "loose", orbit will allow determination of the asteroid mass and, with the imaging data, the rotation state. The medium orbit will allow determination of the gravity field to about degree 4. The low altitude, or "tight" orbit, will be used to measure the gravity field to degree and order 12. The science objective is to measure the bulk density to better than 1%, which will permit constraints on the interior structure. The data is gathered via the tracking, telemetry and command system utilizing a 100 W traveling wave tube amplifier and a fixed 1.5 m high-gain antenna. 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 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.

Alternate Names

  • Dawn/RadioScience


  • Planetary Science: Small Bodies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Alexander S. KonoplivPrincipal InvestigatorNASA Jet Propulsion
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