Using restored two-dimensional X-ray images to reconstruct the three-dimensional magnetopause
Rongcong Wang, Jiaqi Wang, Dalin Li, Tianran Sun, Xiaodong Peng, Guo Yihong
Abstract
Astronomical imaging technology is a basic tool for the exploration of the universe, providing basic data for the research of astronomy and space physics. The soft X-ray imager (SXI) carried by the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) aims to capture 2-D images of the Earth's magnetosheath using soft X-ray imaging. However, the observed 2-D images are affected by many noise factors, destroying the contained information, which is not conducive to the subsequent reconstruction of the 3-D structure of the magnetopause. The analysis of SXI simulated observation images shows that such damage cannot be evaluated with traditional restoration models, which makes it difficult to establish the mapping relationship between SXI simulated observation images and target images using mathematical models. We propose an image restoration algorithm for SXI-simulated observation images, which can recover large-scale magnetospheric structure information. The idea is to train a patch estimator by selecting noise-clean patch pairs with the same distribution through the Classification-Expectation Maximization (CEM) algorithm to achieve the restoration estimation of the SXI simulated observation image, whose mapping relationship with the target image is established by the patch estimator. CEM is used to select multiple patch clusters with the same distribution and train different patch estimators, so as to improve the accuracy of the estimator. Experimental results show that our image restoration algorithm is superior to other classical image restoration algorithms in the SXI simulated observation image restoration task, according to the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM). The restoration results of SXI simulated observation images are used in the tangent fitting approach (TFA) and computed tomography approach (CTA) to magnetospheric reconstruction techniques, significantly improving the reconstruction results. Hence the proposed technology may be feasible for processing SXI-simulated observation images.