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Parametric Dielectric Model Of Comet 67p/churyumov-gerasimenko: Implications On Sounding Cometary Nucleus Using Radar Tomography

Abstract : The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) onboard the ROSETTA mission will probe the nucleus of comet 67P/Churyumov-Gerasimenko in 2014. The variations in signal attenuations to be observed in the 90 MHz-radar tomographies is expected to depend mainly on the three-dimensional variations of the dielectrical properties of the cometary material as a function of porosity, temperature, and mineralogical composition. To explore the parametric space associated with the variations of these parameters and their impacts on the observed dielectrical properties inverted from the CONSERT data, we use the current state of knowledge from the observations made by Tempel-1 and Hayabusa to develop parametric dielectric models of possible internal structures of 67P/C-G. The first model reflects the layered-pile structure proposed by Belton et al. (2007), and the second reflects the rubble-pile model proposed by Weissman et al. (1986). The relative complex dielectric permittivities assigned to each dielectric model are based on laboratory measurements of chondrite dust/water ice mixtures, and are varied as a function of dust fraction, porosity and temperature. For the layered pile model, where porosity is assumed constant at the level of 70% and temperature 20m below the surface is 40 K, the dielectric constant varies mainly as a function of dust fraction, ranging between 4.386-i0.0121 in the pure surface dust mantle to 2.081-i0.000182 in one of the inner ice-rich layers. The modeled dielectric permittivities are consistent with the expected deep penetration of the CONSERT wave through the nucleus. Preliminary results suggest that the changes in the physical properties of the nucleus induce substantial variation in the dielectric properties of cometary material that can be identified in the radar tomography.
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https://hal-insu.archives-ouvertes.fr/insu-00361660
Contributor : Béatrice Pibaret-Bourdon <>
Submitted on : Monday, February 16, 2009 - 12:56:40 PM
Last modification on : Friday, September 25, 2020 - 11:20:11 AM

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  • HAL Id : insu-00361660, version 1

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Tiffany Kataria, Essam Heggy, Stephen Clifford, J. Lasue, Wlodek Kofman. Parametric Dielectric Model Of Comet 67p/churyumov-gerasimenko: Implications On Sounding Cometary Nucleus Using Radar Tomography. American Astronomical Society, 40th DPS meeting, Oct 2008, Ithaca, New York, United States. pp.16.17. ⟨insu-00361660⟩

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