Squared visibilities on ζ Ori A versus time during the night of 2017 Oct 12. From top to bottom panels: baselines S2S1, S2W2, and S1W2 for the reference star κ Ori (blue dots), the target ζ Ori A (cyan diamonds), the squared instrumental visibilities (green crosses), and the transfer function obtained from a linear adjustment (red curve). The last plot is the evolution of the r₀ during the observation.