Trend of (S/N)_θ as a function of (upper panel) and of the integration time (lower panel). Solid curves correspond to the cases in which the normalised baseline of the first measurement is at d₁ /d₀ = 0.0, and dashed curves correspond to the cases in which the baseline of the first measurement is at d₁/d₀ = 0.3 (value chosen to ensure a clear separation between the dashed and continuous curves). The differently coloured curves depend on the normalised baseline of the second measurement.