Tomographic reconstruction of “CME2” from the CME Challenge. (a) Ground-truth electron-density slices at 35° latitude and 60° longitude; the blue dashed lines mark the slice locations (−20°, −10°, 0°, 10°, 20° relative to central longitude). (b)–(d) Reconstructed slices obtained from two-, three-, and four-viewpoint configurations. Observer locations are indicated by blue arrows. Note that the latitude slices are not plane-parallel but correspond to conical surfaces at constant latitude.