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 deg2 field of view and reaches a 10-σ 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 103 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.

Introduction
System Characteristics
    Site and Instrument Overview
    System Operation and Data Reduction
Performance Evaluation
    Optical Performance
    Photometric Calibration
    Limiting Magnitude
    Sample Light Curves
SOLO Operations Toward the SPHEREx SSOC
Acknowledgments
References

• Bumhoo Lim(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea) Corresponding author
• Seungwon Choi(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Masateru Ishiguro(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea) Corresponding author
• Jinguk Seo(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Sihu Ahn(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Hangbin Jo(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Yoonsoo P. Bach(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Sunho Jin(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Carey M. Lisse(Johns Hopkins University Applied Physics Laboratory, MD 20723, USA)
• Max Mahlke(Université Marie et Louis Pasteur, CNRS, Institut UTINAM (UMR 6213), équipe Astro, F-25000 Besançon, France)
• Jooyeon Geem(Asteroid Engineering Laboratory, Luleå University of Technology, Kiruna, Sweden)