Simulated SPHEREx spectra of asteroids and their implications for asteroid size and reflectance estimation

We describe the construction and analysis of simulated SPHEREx spectra of Main Belt and Trojan asteroids. SPHEREx will deliver the first all-sky spectral survey at 96 spectral channels between 0.75 μm and 5.0 μm. We have developed a method for correcting SPHEREx asteroid spectra for intrinsic rotational variability that does not require light curves and can enable studies before LSST light curves become available for this purpose. Using these spectra, we predict that SPHEREx will deliver meaningful flux measurements for about 100,000 asteroids, including close to 10,000 objects with high-quality spectra; this dataset will represent an increase over our current sample size by more than an order of magnitude. The main SPHEREx contribution to asteroid science will be derived from taxonomic classifications, detailed spectroscopic analyses involving a number of diagnostic spectral features associated with olivine, pyroxene, hydroxyl, water ice, and organics, and constraints on thermal properties. We argue that all asteroids with currently known orbits, about a million objects, should be included in the SPHEREx forced photometry object list to maximize its science impact. Our tools and the library of simulated spectra are made publicly available.