SOLO: wide-field asteroid light curve monitoring system for SPHEREx

Bumhoo Lim; Seungwon Choi; Yoonsoo P. Bach; Masateru Ishiguro; Sunho Jin; Carey M. Lisse; Max Mahlke; Jooyeon Geem; Jinguk Seo; Sihu Ahn; Hangbin Jo

arXiv · 2602.08037

SOLO: wide-field asteroid light curve monitoring system for SPHEREx

Bumhoo Lim·Seungwon Choi·Yoonsoo P. Bach·Masateru Ishiguro·Sunho Jin·Carey M. Lisse·Max Mahlke·Jooyeon Geem·Jinguk Seo·Sihu Ahn·Hangbin Jo

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Abstract

We present the Solar system Objects Light curve Observatory (SOLO), a wide-field, high-cadence optical survey system designed to obtain absolutely calibrated asteroid light curves, converted to the Gaia G-band photometric system, in support of the SPHEREx Solar System Object Catalog (SSOC). SOLO was installed at the Sierra Remote Observatories (SRO) in California, USA, in July 2025 and is optimized for continuous, multi-night monitoring of asteroid brightness variations. We describe the system configuration, remote operation, and data reduction pipeline, and evaluate its optical and photometric performance using commissioning data. SOLO achieves stable photometric calibration across the 11.6 deg^2 field of view and reaches a 10-sigma limiting magnitude of G ~ 17.5 for a 180 sec exposure. Sample asteroid light curves obtained over multiple nights demonstrate consistent absolute photometry at the same rotational phase, validating the estimated performance. Finally, we outline the planned operational use of SOLO in connection with NASA's SPHEREx mission. Full science operations of SOLO are scheduled to begin in January 2026. Using these data, we aim to obtain on the order of 10^3 absolutely calibrated asteroid light curves per year in the Gaia G-band, which will be used to support the construction and scientific utilization of the SPHEREx SSOC.

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Bumhoo Lim, Seungwon Choi, Yoonsoo P. Bach, Masateru Ishiguro, Sunho Jin, Carey M. Lisse, Max Mahlke, Jooyeon Geem, Jinguk Seo, Sihu Ahn, Hangbin Jo. 2026-02-08. SOLO: wide-field asteroid light curve monitoring system for SPHEREx. https://arxiv.org/abs/2602.08037

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