Focus on BAO features: the perturbation power spectrum with error bands for survey 2, which is the 3D 21 cm intensity map. The outer (red) errors are for the nominal 48-day observing first pass (survey 2a). The inner (blue) error band is for a two-year observing run (survey 2b) assuming that the data integrate down and full sensitivity is achieved and thus the errors on the power spectrum decrease inversely with observing time.