# # Program information file # PROGRAM_ID 2024A041 PROGRAM_TITLE Characterizing the surface of [1566] Icarus with SpeX and MIRSI PROGRAM_INV1 Eric MacLennan PROGRAM_INV2 Anne Virkki PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT near-Earth objects PROGRAM_ABSTRACT_BEG We propose to observe the near-Earth asteroid [1566] during an upcoming window of opportunity in which it is observable from Earth across an extreme range of solar phase angles [90 degrees down to ~7 degrees]. Our campaign will use the SpeX spectrometer and an upgraded MIRSI instrument to measure changes in the near-infrared spectral slope [i.e., phase reddening] and in the thermal emission [with simultaneous optical photometry] at 10 microns. These datasets acquired in different wavelength regimes will be used to model the surface properties of Icarus, such as the albedo, small-scale roughness, and regolith particle size. As phase reddening is thought to be a consequence of multiple scattering of light from high albedo particles, the spectra collected across many phase angles can be used to model and constrain the surface roughness and particle size. Comparison will also be made to laboratory phase reddening measurements of ordinary chondrite meteorites. Our proposed MIRSI observations will be used to detect changes in the thermal emission from Icarus, which depend on the surface roughness at the centimeter scale as suggested by a thermophysical model. Our SpeX observations will be carried out at five distinct phase angles [runs], and the MIRSI observations will occur during three of these runs. Icarus will be bright enough to reach a high signal-to-noise using Prism mode and thus measure the spectral slope to a high precision. We will account and control for systematic and random [observational] effects that could skew the spectral slope including possible rotational variation of the asteroid. We will push the sensitivity of MIRSI to its quoted detection limit by integrating over an hour on Icarus [250 mJy or brighter]. Guiding using the MIRSI optical camera will be critical for image stacking and for absolute-calibrated photometry that will be used to calculate the surface albedo. PROGRAM_ABSTRACT_END