Modeling and analyzing of time-resolved satellite infrared spectrum based on ground-based detector
Authors: Gu Mu , Ren Qi-Feng , Zhou Jin-Mei , Liao Sheng ,   Institute of Optics and Electronics Chinese Academy of Sciences, Chengdu 610209, China,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Satellite infrared spectra based on ground-based detector are affected by complex factors such as satellite surface temperature, solar radiation, observation angle, etc, whose change cannot be detected in external field experiment. Therefore, it is impossible to analyze what are the main factors that affect the satellite infrared spectra. At the same time, due to the lack of physical information about the satellites through the external field experiment, the validity and physical significance of retrieving features from satellite infrared spectrum cannot be explained. In view of the above problem, a method to model and analyze satellite thermal infrared spectra based on ground-based detector is proposed. It is a feasible research method to accurately establish satellite thermal infrared spectrum model based on the ground detection, then to analyze the simulated infrared spectrum data. Firstly, considering the solar radiation, earth radiation, detectable range of the satellite on the detector, observation angle, atmospheric attenuation, etc., the satellite thermal infrared spectrum model can be established more accurately. Then, taking FY-3 satellite for example, the physical and orbital parameters of the satellite are set up, and the 3−14<inline-formula><tex-math id="M500">\begin{document}${\text{μ}}{\rm m}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20181933_M500.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20181933_M500.png"/></alternatives></inline-formula> infrared irradiance of the satellite on the pupil of the detector is calculated by using the model. Meanwhile, the main factors affecting the infrared spectrum of the satellite are analyzed. Finally, the equivalent temperature and equivalent area are extracted by fitting the satellite infrared spectrum with the Planck formula. And they are compared with the physical properties of the satellite. The results show that among the various factors, with the satellite’ movement, the change of the visible state of the satellite induced by the satellite’s movement is the main factor that affects the satellite infrared spectrum. The physical meanings of the equivalent temperature and equivalent area can also be explained effectively. The equivalent temperature is close to the temperatures of the solar panels, and their temperature difference is only about 15 K. The change of equivalent area is consistent with that of the satellite projected area. Moreover, it is also found that there is a large temperature difference between the solar panels and the body, which makes their infrared spectra obviously different. Therefore, it is hopeful to obtain the areas and temperatures of the solar panels and the body respectively. This research can make up for the shortcomings of the external field experiments and promote the monitoring and recognizing of satellites by ground-based infrared detectors.