Left: 3-σ sensitivity versus separation for a completeness level of 80%. Right: completeness in the separation range 6−40 mas versus contrast. Simulations are for a single snapshot pointing (dashed lines) and for five pointings separated by one hour (solid lines). Colours are for the four configurations of VLTI displayed in Fig. 1. The contrast axes can be scaled for any given accuracy of the closure phase measurements (here σ = 0.25deg).