Radar properties of comets: Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko

Essam Heggy, Elizabeth M. Palmer, Wlodek Kofman, Stephen M. Clifford, Kevin Righter, Alain Hérique

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

In 2014, the European Space Agency's Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta's CONSERT experiment aims to explore the cometary nucleus' geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the dielectric properties of the comet nucleus and how they vary with the spatial distribution of geophysical parameters. Using observations of Comets 9P/Tempel 1 and 81P/Wild 2 in combination with dielectric laboratory measurements of temperature, porosity, and dust-to-ice mass ratio dependencies for cometary analog material, we have constructed two hypothetical three-dimensional parametric dielectric models of Comet 67P's nucleus to assess different dielectric scenarios of the inner structure. Our models suggest that dust-to-ice mass ratios and porosity variations generate the most significant measurable dielectric contrast inside the comet nucleus, making it possible to explore the structural and compositional hypotheses of cometary nuclei. Surface dielectric variations, resulting from temperature changes induced by solar illumination of the comet's faces, have also been modeled and suggest that the real part of the dielectric constant varies from 1.9 to 3.0, hence changing the surface radar reflectivity. For CONSERT, this variation could be significant at low incidence angles, when the signal propagates through a length of dust mantle comparable to the wavelength. The overall modeled dielectric permittivity spatial and temporal variations are therefore consistent with the expected deep penetration of CONSERT's transmitted wave through the nucleus. It is also clear that changes in the physical properties of the nucleus induce sufficient variation in the dielectric properties of cometary material to allow their inversion from radar tomography.

Original languageEnglish
Pages (from-to)925-939
Number of pages15
JournalIcarus
Volume221
Issue number2
DOIs
Publication statusPublished - Nov 2012
Externally publishedYes

Fingerprint

comets
comet
radar
comet nuclei
modeling
nuclei
dust
dielectric property
mass ratios
dielectric properties
ice
tomography
Rosetta mission
Tempel 1 comet
permittivity
inversions
porosity
rendezvous
European Space Agency
spatial distribution

Keywords

  • Comets, Composition
  • Comets, Dust
  • Experimental techniques
  • Ices
  • Radar observations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Heggy, E., Palmer, E. M., Kofman, W., Clifford, S. M., Righter, K., & Hérique, A. (2012). Radar properties of comets: Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko. Icarus, 221(2), 925-939. https://doi.org/10.1016/j.icarus.2012.09.023

Radar properties of comets : Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko. / Heggy, Essam; Palmer, Elizabeth M.; Kofman, Wlodek; Clifford, Stephen M.; Righter, Kevin; Hérique, Alain.

In: Icarus, Vol. 221, No. 2, 11.2012, p. 925-939.

Research output: Contribution to journalArticle

Heggy, E, Palmer, EM, Kofman, W, Clifford, SM, Righter, K & Hérique, A 2012, 'Radar properties of comets: Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko', Icarus, vol. 221, no. 2, pp. 925-939. https://doi.org/10.1016/j.icarus.2012.09.023
Heggy, Essam ; Palmer, Elizabeth M. ; Kofman, Wlodek ; Clifford, Stephen M. ; Righter, Kevin ; Hérique, Alain. / Radar properties of comets : Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko. In: Icarus. 2012 ; Vol. 221, No. 2. pp. 925-939.
@article{4af5c16b35ef4c019bb5a06fb63c0e32,
title = "Radar properties of comets: Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko",
abstract = "In 2014, the European Space Agency's Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta's CONSERT experiment aims to explore the cometary nucleus' geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the dielectric properties of the comet nucleus and how they vary with the spatial distribution of geophysical parameters. Using observations of Comets 9P/Tempel 1 and 81P/Wild 2 in combination with dielectric laboratory measurements of temperature, porosity, and dust-to-ice mass ratio dependencies for cometary analog material, we have constructed two hypothetical three-dimensional parametric dielectric models of Comet 67P's nucleus to assess different dielectric scenarios of the inner structure. Our models suggest that dust-to-ice mass ratios and porosity variations generate the most significant measurable dielectric contrast inside the comet nucleus, making it possible to explore the structural and compositional hypotheses of cometary nuclei. Surface dielectric variations, resulting from temperature changes induced by solar illumination of the comet's faces, have also been modeled and suggest that the real part of the dielectric constant varies from 1.9 to 3.0, hence changing the surface radar reflectivity. For CONSERT, this variation could be significant at low incidence angles, when the signal propagates through a length of dust mantle comparable to the wavelength. The overall modeled dielectric permittivity spatial and temporal variations are therefore consistent with the expected deep penetration of CONSERT's transmitted wave through the nucleus. It is also clear that changes in the physical properties of the nucleus induce sufficient variation in the dielectric properties of cometary material to allow their inversion from radar tomography.",
keywords = "Comets, Composition, Comets, Dust, Experimental techniques, Ices, Radar observations",
author = "Essam Heggy and Palmer, {Elizabeth M.} and Wlodek Kofman and Clifford, {Stephen M.} and Kevin Righter and Alain H{\'e}rique",
year = "2012",
month = "11",
doi = "10.1016/j.icarus.2012.09.023",
language = "English",
volume = "221",
pages = "925--939",
journal = "Icarus",
issn = "0019-1035",
publisher = "Academic Press Inc.",
number = "2",

}

TY - JOUR

T1 - Radar properties of comets

T2 - Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko

AU - Heggy, Essam

AU - Palmer, Elizabeth M.

AU - Kofman, Wlodek

AU - Clifford, Stephen M.

AU - Righter, Kevin

AU - Hérique, Alain

PY - 2012/11

Y1 - 2012/11

N2 - In 2014, the European Space Agency's Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta's CONSERT experiment aims to explore the cometary nucleus' geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the dielectric properties of the comet nucleus and how they vary with the spatial distribution of geophysical parameters. Using observations of Comets 9P/Tempel 1 and 81P/Wild 2 in combination with dielectric laboratory measurements of temperature, porosity, and dust-to-ice mass ratio dependencies for cometary analog material, we have constructed two hypothetical three-dimensional parametric dielectric models of Comet 67P's nucleus to assess different dielectric scenarios of the inner structure. Our models suggest that dust-to-ice mass ratios and porosity variations generate the most significant measurable dielectric contrast inside the comet nucleus, making it possible to explore the structural and compositional hypotheses of cometary nuclei. Surface dielectric variations, resulting from temperature changes induced by solar illumination of the comet's faces, have also been modeled and suggest that the real part of the dielectric constant varies from 1.9 to 3.0, hence changing the surface radar reflectivity. For CONSERT, this variation could be significant at low incidence angles, when the signal propagates through a length of dust mantle comparable to the wavelength. The overall modeled dielectric permittivity spatial and temporal variations are therefore consistent with the expected deep penetration of CONSERT's transmitted wave through the nucleus. It is also clear that changes in the physical properties of the nucleus induce sufficient variation in the dielectric properties of cometary material to allow their inversion from radar tomography.

AB - In 2014, the European Space Agency's Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta's CONSERT experiment aims to explore the cometary nucleus' geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the dielectric properties of the comet nucleus and how they vary with the spatial distribution of geophysical parameters. Using observations of Comets 9P/Tempel 1 and 81P/Wild 2 in combination with dielectric laboratory measurements of temperature, porosity, and dust-to-ice mass ratio dependencies for cometary analog material, we have constructed two hypothetical three-dimensional parametric dielectric models of Comet 67P's nucleus to assess different dielectric scenarios of the inner structure. Our models suggest that dust-to-ice mass ratios and porosity variations generate the most significant measurable dielectric contrast inside the comet nucleus, making it possible to explore the structural and compositional hypotheses of cometary nuclei. Surface dielectric variations, resulting from temperature changes induced by solar illumination of the comet's faces, have also been modeled and suggest that the real part of the dielectric constant varies from 1.9 to 3.0, hence changing the surface radar reflectivity. For CONSERT, this variation could be significant at low incidence angles, when the signal propagates through a length of dust mantle comparable to the wavelength. The overall modeled dielectric permittivity spatial and temporal variations are therefore consistent with the expected deep penetration of CONSERT's transmitted wave through the nucleus. It is also clear that changes in the physical properties of the nucleus induce sufficient variation in the dielectric properties of cometary material to allow their inversion from radar tomography.

KW - Comets, Composition

KW - Comets, Dust

KW - Experimental techniques

KW - Ices

KW - Radar observations

UR - http://www.scopus.com/inward/record.url?scp=84867810391&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84867810391&partnerID=8YFLogxK

U2 - 10.1016/j.icarus.2012.09.023

DO - 10.1016/j.icarus.2012.09.023

M3 - Article

AN - SCOPUS:84867810391

VL - 221

SP - 925

EP - 939

JO - Icarus

JF - Icarus

SN - 0019-1035

IS - 2

ER -