Characterizing the regolith of a broad sample of near-Earth asteroids (NEAs) is necessary to understand their ensemble properties. Our team combines high-fidelity shape models and near-IR spectra obtained over multiple viewing geometries with our thermophysical model to describe the properties of NEA surfaces in greater detail than possible with simpler approaches. We utilize observations of both thermal emission and surface reflectance, which allows for the thermal and scattering properties of different regions on the surface to be investigated and enables a better understanding of any surface heterogeneity in addition to the global properties.
We present results from our investigation of (433) Eros, the target of the NEAR Shoemaker mission. We obtained near-IR spectra of Eros using the NASA/IRTF SpeX instrument in LXD 1.9 mode (1.9-4.2 μm) over 3 epochs in 2009-2011 and LXD Long mode (1.98-5.3 μm) over 23 epochs in 2018-2019. We also analyzed published IRTF SpeX LXD 1.9 data from 6 additional epochs in 2011-2012 (Rivkin et al. 2018), as well as 3 epochs of published mid-IR 8-13 μm spectra of Eros taken with Spectrocam-10 on the 200” Hale telescope at Palomar Observatory in 2002 (Lim et al. 2005). These 35 spectra probe a variety of rotation phases and illumination geometries, allowing us to constrain Eros’s properties at the hemispherical, and in one case sub-hemispherical, level. NEAR’s in situ measurements of Eros’s shape and topography allow us to connect our ground-based thermal spectra to the thermal properties of specific locations, as well as to better constrain Eros’s global-average thermal properties. Previous ground-based thermal observations of Eros examined a limited number of rotational phases; this work combines some of those data with our new dataset to produce a rotationally-resolved, multi-wavelength thermophysical model of Eros’s surface. We will show results from our thermophysical modeling of Eros using our code SHERMAN (Magri et al. 2018) and discuss variations of Eros’s thermal emission over the surface and what that implies for surface heterogeneity.