Boundary Detection in Three Dimensions With Application to the SMILE Mission: The Effect of Photon Noise

Imaging magnetospheric satellite missions provide information, which is complementary to in situ observations. Imaging is often able to provide an instantaneous picture of large-scale structures, whereas in situ measurements, even multipoint in situ measurements, can only provide an average view of large-scale structure. But imaging also presents some challenges. When three-dimensional structures need to be extracted from two-dimensional images, it is necessary to either make suitable assumptions or record a large enough number of images from different viewing geometries to allow a reconstruction (e.g., tomography). Imaging data exist over a wide range of sources including visible light, ultraviolet light, extreme ultraviolet, energetic neutral atoms, and X-rays, each informing different physical mechanisms. In this paper we consider the extraction of the geometry of the magnetopause and the bow shock from single X-ray images expected from the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. We examine the effect of photon-counting noise in determining the boundary geometries. We also consider the effect of different viewing geometries in the form of orbital vantage point and target look direction. Finally, we consider the effect of background noise. We find that our approach is relatively robust to viewing geometry effects and works at low count rates.