How accurately can we find the magnetopause standoff distance using SMILE SXI?

The joint mission between the European Space Agency and the Chinese Academy of Sciences, the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE), is due to launch in spring 2026. The Soft X-ray Imager (SXI) on board SMILE will measure X-rays emitted from the magnetosheath and cusps. These data will help trace variations in the positions of the magnetopause and cusps in response to changes in the solar wind. We present a fast, computationally inexpensive method for determining the magnetopause standoff distance using a set of simulated X-ray images. We demonstrate that the standoff distance can be obtained with an accuracy better than 0.5 RE using a 1-minute integration time when the magnetosphere is significantly compressed. We also discuss the differences between emissions produced by the magnetosheath and the cusps, as well as the role of spacecraft position in SXI data analysis.