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

TL;DR

The paper introduces SOLO, a high-cadence, wide-field optical survey system designed to obtain calibrated asteroid light curves in support of the SPHEREx mission, with demonstrated stable photometry and planned operational deployment.

Contribution

This work presents the design, implementation, and initial performance evaluation of SOLO, a novel system for continuous asteroid monitoring in support of space-based infrared surveys.

Findings

Achieves stable photometric calibration across an 11.6 deg^2 field.

Reaches a 10-sigma limiting magnitude of G ~ 17.5 in 180 sec.

Demonstrates consistent asteroid light curves over multiple nights.

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.