Data analysis and foreground removal algorithms for 21-cm cosmology experiments

Cosmology experiments using the highly redshifted 21-cm line of hydrogen are taking a range of observational and instrumental approaches. The simplest, at first sight, are experiments aimed at measuring the sky-averaged (`global´) signal using a single, well-characterized and precisely calibrated antenna, either on the ground or in space. Multiple-antenna and interferometric global signal experiments aim to trade off the increased complexity against improved resolution, and a better handle on e.g. the behaviour of the ionosphere and the instrumental beam. Studying the 21-cm fluctuations requires interferometry but still allows for many different approaches, e.g. using drift scans versus tracking individual fields, using redundant baselines versus aiming for minimal redundancy, or trading data volume against uv coverage and field of view.