Abstract: The Soft X-ray Imager (SXI) on board the forthcoming mission Solar wind – Magnetosphere Ionosphere Link Explorer (SMILE) will receive a set of soft X-ray images that contain information about magnetopause dynamics in response to solar wind variations. We use the results of MHD simulations and the software simulator sxi_sim developed at the University of Leicester to yield the SXI images for different solar wind conditions. In particular, we simulate an event with a southward interplanetary magnetic field (IMF) turning and produce SXI count maps with a five minute integration time. Making assumptions about the magnetopause shape, we find the magnetopause standoff distance from the count maps and compare it with the one obtained directly from the MHD simulation. We demonstrate that the change in the magnetopause standoff distance can be accurately reconstructed by our method for a given spacecraft position near apogee.