The (u, v) coverage of the combined 5 epoch data set for J0906+6930 at 2.3 GHz. The points indicate the baseline lengths projected onto a plane perpendicular to the geocentric vector pointing towards the radio source. The u (east–west) and v (north–south) axes are conventionally scaled in the units of million wavelengths (λ). The nearly circular shape of the (u, v) coverage is caused by the northern hemisphere array observing a circumpolar source at high declination, and the tracks covering full days.