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Titel |
Dwarf Planet Ceres: Preliminary Surface Temperatures from Dawn |
VerfasserIn |
Federico Tosi, Maria Teresa Capria, Maria Cristina De Sanctis, Eleonora Ammannito, Fabrizio Capaccioni, Francesca Zambon, Andrea Raponi, Christopher T. Russell, Carol A. Raymond |
Konferenz |
EGU General Assembly 2015
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 17 (2015) |
Datensatznummer |
250111816
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Publikation (Nr.) |
EGU/EGU2015-11960.pdf |
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Zusammenfassung |
After a 7-year cruise, and a 1-year successful mission at asteroid 4 Vesta, the Dawn
spacecraft is about to enter orbit around its second and final goal, the dwarf planet
Ceres. In the mission phases that have been planned, the VIR imaging spectrometer
aboard Dawn will acquire a large amount of hyperspectral data of the surface, to map
the surface composition and to retrieve surface temperatures on the dayside of the
target.
The thermal behavior of the surface of dwarf planet Ceres is related to composition and
physical properties that provide information about the nature and evolution of surface
materials. The maximum temperature with the Sun overhead was estimated from
measurements and modeling to be 235±4 K at 2.77 AU, i.e. comparable to the
maximum surface temperature measured by the Rosetta spacecraft on the small
asteroid Steins during the close flyby occurred in September 2008. The infrared range
longward of Â3.5 μm is crucial to reveal the thermal emission of Ceres on its dayside,
which can be used to map surface temperature across different orbits and local
solar times (LST), and therefore constrain thermal properties at different spatial
scales.
Here we show the first spatially-resolved temperature data of dwarf planet Ceres derived in
the Approach phase carried out in January and February 2015, with the target seen over tens
of VIR pixels in the overall spatial resolution range between 50 km/px and 12.5 km/px (since
February 2015, the VIR spatial resolution is better than any observation carried out by the
Hubble Space Telescope and the Keck telescope). Broadly regional trends can be derived in
this way, waiting for higher resolution coverage that will be achieved at later stages of the
mission, under variable phase angles, illumination conditions, and heliocentric
distances.
To derive surface temperature, we rely on a Bayeasian approach to nonlinear inversion that
was applied to the entire dataset of infrared data acquired by the VIR mapping spectrometer
aboard the Dawn spacecraft during its orbital phase at asteroid Vesta in 2011-2012, as well as
to Rosetta/VIRTIS data obtained during the close flyby of asteroid 21 Lutetia in 2010 and to
comet 67P/Churyumov-Gerasimenko in the mapping phase carried out since July 2014. This
approach allows simultaneous retrieval of surface temperature and emissivity in the 4.5-5.1
μm range.
VIR cannot measure temperatures on the nightside of Ceres, as well as in the northern polar
region that will undergo permanent shadowing conditions throughout Dawn’s nominal orbital
mission phases.
Acknowledgements: This work was supported by the Italian Space Agency (ASI),
ASI-INAF Contract I/004/12/0. Support of the Dawn Science, Instrument, Operations Teams,
as well as of the Dawn at Vesta Participating Scientist program, is gratefully acknowledged.
The computational resources used in this research have been supplied by INAF-IAPS through
the DataWell project. |
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