Infrared and Laser Engineering, Volume. 54, Issue 6, 20240574(2025)

Research on the on-orbit calibration method for spaceborne infrared spectral imager using dual blackbodies

Yunmeng LIU1,2,3, Yang WANG1,3, Lei DING1,3、*, Huixian DUAN1,3, and Jinguang CHAI1,3
Author Affiliations
  • 1Shanghai Institute of Technical Physics Chinese Academy of Sciences, Shanghai 200083, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
  • 3Technology Innovation Center of Metrology Technology of Infrared Remote Sensing, State Administration for Market Regulation, Beijing 102200, China
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    ObjectiveThe primary objective of this study is to address the effectiveness in improving the calibration accuracy of the low-temperature part based on the low-temperature blackbody. With the improvement of inversion accuracy of the ground object target from remote sensing, the quantitative level of the spaceborne equipment is increasing. Typically, on-board blackbody, variable-temperature blackbody, or reference blackbody are installed to solve the problems of on-orbit calibration and reference transfer measurements. From the ground applications, the temperature field of on-orbit instruments is different from tank, it means that the calibration coefficients obtained before launch cannot be directly applied to on-orbit calibration equations. Consequently, the on-orbit calibration coefficients calculated using two-point method based on the "on-board blackbody + cold space" exits significant deviations, especially for detecting targets below 200 K. Therefore, in order to enhance the inversion accuracy at the low-temperature infrared spectrum, a low-temperature blackbody is added to calibrate combined with the on-board blackbody.MethodsFor the center wavelengths of 10.8 μm and 12 μm, the in-orbit calibration method using the dual blackbody for spaceborne infrared spectral imager is researched, and the fusion calibration of "on-board blackbody+low-temperature blackbody", "low-temperature blackbody+cold space" and "on-board blackbody+cold space" is proposed. Based on the in-orbit calibration data, the calibration accuracy and the response consistency of the fusion calibration method for spaceborne infrared spectral imager are analyzed, combined with the laboratory calibration data. Firstly, using the two-point fitting method based on "low-temperature blackbody+on-board blackbody" the temperature deviations at different radiation targets are calculated (Fig.3-Fig.4). It is shown that when the errors of the two blackbodies remain constant, the larger temperature difference between the low-temperature and on-board blackbodies can lead to the smaller inversion errors, while a smaller temperature difference can lead to the greater extrapolated radiance deviations. Similarly, using the two-point fitting methods based on "cold space+on-board blackbody" and "low-temperature blackbody+cold space", temperature deviations at various radiation targets are calculated (Fig.6, Fig.8). The results indicate that the "low-temperature blackbody+cold space" calibration method produces relatively consistent temperature deviations at the low-temperature section compared to the "on-board blackbody+cold space", but exhibits larger deviations at high-temperature section @350 K. Additionally, the response consistency of the infrared detection systems before and after launch is calculated (Tab.1), it is shown that the responsivity ratio of dual blackbodies using on-orbit calibration method and pre-launch calibration method is consistent. Finally, based on 370 sample datasets, on-orbit calibration coefficients of the infrared detection system are calculated using the two-point method with three calibration sources: low-temperature blackbody, on-board blackbody, and cold space. The radiance of Earth’s low-temperature targets is computed (Fig.11, Fig.13) to analyse the calibration effectiveness.Results and DiscussionsThrough extensive experiments, it is found that: the brightness temperature results calculated using "on-board blackbody+low-temperature blackbody", "low-temperature blackbody+cold space" and "on-board blackbody+cold space" are different in the low-temperature region, the brightness temperature results calculated using "low-temperature blackbody+cold space" and "on-board blackbody+cold space" are approximate; The calibration accuracy using "on-board blackbod+low-temperature blackbody” is depended on the calibration accuracy of two blackbodies, the calibration accuracy using "low-temperature/on-board blackbody+cold space" is depended on the calibration accuracy of the blackbody and cold space energy. To acquire more accurate radiance of the cold space, the low-temperature blackbody should be controlled to 180 K. When the blackbody calibration error is 0.5 K, a calibration accuracy of 0.5 K can be achieved for the low-temperature section of radiation targets.ConclusionsAccording to the laboratory calibration data and the on-orbit calibration data, before and after injection, the response of the on-board blackbody and the low-temperature blackbody is consistent using the current calibration scheme. Based on the on-orbit calibration data, through the fusion calibration method—"on-board blackbody+low-temperature blackbody", "on-board blackbody+cold space", and "low-temperature blackbody+cold space”, it is found that the brightness temperature results from the "on-board blackbody+cold space” and "low-temperature blackbody+cold space” are similar, they all have calibration differences in low-temperature region. To obtain a more detailed low-temperature nonlinear curve, it is necessary to increase the dynamic range of the low-temperature blackbody, and the temperature at the lower-temperature part is below 180 K.

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    Yunmeng LIU, Yang WANG, Lei DING, Huixian DUAN, Jinguang CHAI. Research on the on-orbit calibration method for spaceborne infrared spectral imager using dual blackbodies[J]. Infrared and Laser Engineering, 2025, 54(6): 20240574

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    Paper Information

    Category: Infrared

    Received: Jan. 12, 2025

    Accepted: --

    Published Online: Jul. 1, 2025

    The Author Email:

    DOI:10.3788/IRLA20240574

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