In parallel-beam X-ray CT, a 3D image of an object is reconstructed from a collection of its 2D X-ray projections taken from different angles around a fixed rotation axis. The location of the axis must be estimated accurately or serious artifacts arise during reconstruction. In this project, the student will implement a method (already existing in the literature) for estimating the rotation axis directly from the data and compare its performance to a baseline method on simulated and real data.