Physics
Scientific paper
Mar 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007sptz.prop..292s&link_type=abstract
Spitzer Proposal ID #292
Physics
Scientific paper
We have a unique opportunity to map at subhemispheric resolution the thermophysical properties of the small Earth-crossing aster oid 25143 Itokawa this April/May 2007 by combining high-resolution shape and topography models, recently derived from imagery of the asteroid obtained by the Japanese Hyabusa mission, with rotationally well-sampled thermal spectra obtained with Spitzer IRS. Prior groundbased observations in the N and Q bands (limited in rotational coverage, wavelength coverage, with substantially lower signal-to-noise) provide only a single global value of thermal inertia, compared to the possible 40 surface resolution elements this program may obtain. Itokawa has a block-strewn surface combined with smooth areas with no definitive large craters and an apparent deficiency of small craters - the first clear example of a 'rubble-pile', that may be characteristic of most small NEOs. Itokawa makes its closest and best approach to the Spitzer spacecraft (0.09 AU) in April at an observational phase angle providing an excellent view of the terminator across which surface temperature changes are maximum. Significant changes in shape and spectral peak of Itokawa's SED as the asteroid rotates are s imulated. The high signal-to-noise of the proposed Spitzer IRS observations will well-resolve these spectral differences. Though Itokawa is not spatially resolved by Spitzer, a priori knowledge of its detailed shape and topography from the Hyabusa mission allows us to divide its surface into subunits with independent thermal properties, and constrain them by grid search, finding those values or range of values that reproduce the numerous spectra obtained, where different combinations of surface units contribute to each spectrum as they move from evening to morning to afternoon and in and out of view (sometimes blocked by nearby units). Maximizing rotational sampling maximizes the longitudinal resolution of our thermophysical maps and the number of resolution elements covering its surface.
Abell Paul
Chamberlain Matthew
Domingue Deborah
Gaskell Robert
Lederer Susan
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