Beyond the 2.45 micron Barrier: The SPHEREx Year 1 Census of Asteroid Spectral Diversity

Launched in March 2025, NASA’s SPHEREx mission is currently conducting the first all-sky near-infrared spectral survey at wavelengths between 0.75μm and 5μm.  Over its two-year nominal mission, SPHEREx acquires a spectrum for every 6.2” x 6.2” pixel on the sky, a transformative dataset for its primary science drivers in cosmology, galaxy formation, and interstellar ices [1]. However, this survey also provides an unprecedented opportunity for Solar System science, as exemplified by the recent SPHEREx discovery of a CO2 atmosphere around the interstellar comet 3I/ATLAS [2]. This presentation details the ongoing efforts of the SPHEREx Solar System Object Catalogue (SSOC) External Collaboration (XC) to extract, calibrate, and categorise these spectra, with a focus on the first-year asteroid results.

The scientific significance of the SPHEREx dataset for minor bodies lies in its unique spectral coverage. While previous large-scale taxonomic efforts have focused on silicaceous compositions discernible in ground-based observations between 0.45μm and 2.45μm [3, 4], SPHEREx provides a critical window into the presence of volatiles, organics, and hydrated minerals identified at wavelengths beyond 2.45 μm (e.g. [5]). The sheer volume of high-quality spectra generated by this mission allows for a statistically robust ensemble analysis of the Main Belt and beyond, transitioning from individual case studies toward a holistic characterisation of the Solar System’s compositional landscape [6].

Now, after more than one year of active operations and data processing, the SSOC XC presents a comprehensive status update. We showcase the first intermediate spectra derived from the mission pipeline, spanning diverse taxonomic classes including C-, S-, and M-complex asteroids. Extracting high-fidelity spectra for moving targets from a scanning mission presents unique data-reduction challenges; we discuss our solutions for these issues and address the remaining systematics currently present in the spectral products. Finally, we provide a timeline for the public release of the initial Solar System Object Catalogue.  This work represents a major milestone in planetary astronomy, providing a rich, uniform spectral library that will serve as a cornerstone for Solar System studies for decades to come.