New Method Makes Non-uniformity Calibration for Space Camera Possible (Physics)

The directional polarimetric camera (DPC) developed by Anhui Institute of Optics and Fine Mechanics (AIOFM), Hefei Institutes of Physical Science (HFIPS), is a satellite sensor with the aim to observe the polarization and directionality of the Earth’s reflectance.

For DPC, non-uniformity is reflected in the high frequency difference in the rapid change of adjacent pixels, and the low frequency difference in the overall slow change of different field of view. It’s hard to effectively distinguish these differences by the single correction method.

Recently, a research group led by Prof. HONG Jin from AIOFM proposed a new method based on multi-parameters that realized the non-uniformity calibration of space-borne area charge coupled device (CCD) for DPC.

Using the electro-optical performance measurement system of the CCD detector, they obtained the sensitive factors such as temperature, dark current, exposure time and spectral response.

Fig. 2 Comparison of single frame image before and after PRNU correction (Image by YAO Pingping)

After a series of preprocessing of the image including removal of dark signal and smearing effect, the low-frequency unbalanced response difference of the image surface was eliminated, and the high-frequency difference was effectively suppressed.

“The non-uniformity of a single picture is reduced from 2.86% to 0.36%,” said YAO Pingping, a member of the research team. “After correction, the data noise is shown as shot noise, and the detector has good ability of dynamic range adjustment.”

This research offered data support for the instrumental calibration and in-flight fast calculation, and provided effective reference for the subsequent polarization remote sensing instruments.

Featured image: Schematic of the directional polarimetric camera (Image by YAO Pingping)

Reference: Pingping Yao, Bihai Tu, Sunlong Xu, Xinyu Yu, Zhilong Xu, Donggen Luo, and Jin Hong, “Non-uniformity calibration method of space-borne area CCD for directional polarimetric camera,” Opt. Express 29, 3309-3326 (2021).

Provided by Chinese Academy of Sciences

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