The accurate calibration of infrared absolute radiance payloads is crucial for high-precision space-based measurement, especially for climate monitoring and environmental research. The emissivity of blackbody sources must be carefully determined to ensure the accuracy of infrared radiance measurement from space-based instruments. However, this process faces challenges due to various factors that contribute to measurement uncertainty. In particular, the heated halo structure serving as a key component in infrared radiometric calibration introduces additional complexity in the uncertainty estimation of emissivity measurement. We propose an approach to assessing the uncertainty in the emissivity measurement of the blackbody within an infrared absolute radiance payload based on a heated halo structure. The goal is to optimize the measurement accuracy by identifying key error factors and assessing their propagation via the system.

The measurement system employs a heated halo structure, consisting of an annular thermal radiation source surrounding a blackbody target. The halo is heated to a specific temperature, creating a controlled radiative environment that interacts with the blackbody’s thermal radiation. The blackbody emissivity is determined by analyzing the radiation reflected by the blackbody and reaching a spectrometer, which measures the infrared spectrum emitted from the blackbody. The system is designed to measure the absolute radiance emitted by the blackbody, which is influenced by factors such as temperature variations, spectral sensitivity of the measurement equipment, and geometrical configurations. Meanwhile, an error propagation model is developed to quantify the emissivity measurement uncertainty. The model incorporates various sources of uncertainty, such as the temperature uncertainties of both the blackbody and the heated halo, the spectral response of the spectrometer, and geometrical factors affecting radiation collection. We conduct a simulation to evaluate how each source of uncertainty propagates during the measurement process. By simulating the uncertainties associated with the temperature of the blackbody and halo, as well as the spectrometer’s precision, the model assesses the effect of each factor on the final measurement uncertainty.

Simulation results indicate that several key factors significantly influence the emissivity measurement uncertainty. Among these factors, the temperature uncertainties of the blackbody and heated halo, as well as the spectral sensitivity of the spectrometer, emerge as the most influential factors. The temperature of the blackbody is critical as any fluctuation in its temperature directly affects the emitted radiance. Similarly, uncertainties in the heated halo’s temperature introduce variability in the radiative environment, which can affect the overall measurement precision. Spectrometer sensitivity also plays a crucial role in the uncertainty assessment. The spectrometer’s ability to resolve fine variations in the emitted spectrum is central to accurate radiance measurement. A high-precision spectrometer with low sensitivity errors is essential for minimizing the measurement uncertainty. Additionally, the distance between the blackbody and the heated halo, and the geometric alignment of the components are factors to be optimized for improved measurement accuracy. One of the most critical findings of the simulation is that minimizing the temperature difference between the high and low-temperature states of the heated halo can significantly reduce measurement uncertainty. Further analysis of the system’s geometry reveals that the relative positioning of the blackbody and heated halo affects the radiative exchange between the components. Optimizing the distance between the blackbody and the halo is crucial for minimizing radiative interference and achieving more accurate emissivity measurements. The results also highlight the importance of careful calibration of the spectrometers. The precision of the spectrometer in measuring infrared radiation is critical, as even small errors in spectral measurement can propagate through the system and result in significant uncertainty in emissivity calculation. Fig. 7 presents the combined effects of all uncertainty sources, showing the relative contributions of spectrometer sensitivity and temperature uncertainties. It illustrates the significant influence of temperature uncertainties of the blackbody and the spectral sensitivity of the spectrometer. Meanwhile, Fig. 8 reveals how spectral sensitivity errors affect the final uncertainty, with larger errors in spectral measurement causing higher uncertainty in emissivity determination. Fig. 9 further examines the influence of thermal control on the measurement process. The data suggests that maintaining a stable temperature environment for the blackbody minimizes fluctuations in the measurement, thus improving the emissivity result accuracy. In the conditions allowed by technology, efforts should be made to minimize the temperature uncertainty of the blackbody as much as possible. These results demonstrate that optimizing the spectrometer’s sensitivity and stabilizing the system’s thermal environment are the most effective ways to reduce the emissivity measurement uncertainty.

We provide a comprehensive uncertainty model for measuring the emissivity of blackbody sources in infrared absolute radiance payloads based on a heated halo structure. The findings emphasize the importance of considering multiple sources of uncertainty, including temperature fluctuations, spectrometer sensitivity, and geometrical configurations. By optimizing these factors, significant improvements in measurement accuracy can be achieved. The research results provide essential insights for the design and calibration of high-precision infrared absolute radiance payloads, offering guidance for future space-based climate monitoring missions. The developed model serves as a foundation for enhancing the traceability and reliability of infrared radiance measurements, contributing to the development of more accurate and standardized space-based radiometric systems.