Design of On-orbit Calibration Method for A Lunar-Based Earth Observation Radiometer

Accurate measurement of the Earth’s Radiation Budget （ERB） is essential for understanding global climate change and validating the performance of climate models. However, traditional satellite-borne radiometers face inherent limitations in platform stability, orbital decay, and observational geometry, which hinder their ability to achieve the long-term accuracy and stability required for climate-quality data products. The Moon, as a natural and ultra-stable platform, offers a promising alternative for continuous, full-disk Earth radiation observations. Its unique attributes—including a stable surface, the absence of atmospheric interference, consistent Earth-facing geometry, and predictable thermal environment—make it an ideal base for next-generation Earth observation missions. This paper systematically analyzes the advantages and environmental challenges of the lunar platform and proposes an innovative on-orbit calibration methodology tailored for a Moon-based Earth observation radiometer. The core of the proposed approach integrates a fixed-point blackbody with the deep-space cold source to establish a high-accuracy reference for the infrared channels. For the solar reflective bands, an onboard solar diffuser combined with a high-precision two-axis pointing mechanism is employed to enable frequent radiometric calibration. To monitor the potential degradation of the diffuser’s reflectance, an independent stellar observation strategy is introduced, leveraging the Moon’s excellent astronomical viewing conditions. In addition, a multi-channel consistency check mechanism is established to ensure the self-consistency of the radiometric data across different spectral bands. Cross-validation with other high-accuracy satellite missions （e.g., CLARREO） is also incorporated to maintain international traceability. Furthermore, a comprehensive accuracy traceability chain is constructed, linking pre-launch laboratory calibration, on-orbit reference sources, and natural invariant targets （e.g., pristine lunar regions）, thereby ensuring the long-term reliability of the observed data. This study provides a systematic technical framework and theoretical foundation for the design of calibration systems in future lunar-based and deep-space Earth observation missions, supporting the generation of benchmark climate data records with unprecedented accuracy and stability.