Highly accurate spectroscopic models for O2 A-band [b1S+ ← X3SÀ(0,0)] absorption
are required in numerous satellite- and ground-based remote sensing measurements of atmospheric greenhouse gases. In this study, we quantify the sensitivity of the calculated A-band transmission spectrum to the choice of line profile and model-input line parameter data. The models considered include the Voigt and Galatry profiles for the individual A-band transitions as well as line mixing and collision-induced absorption. In order of increasing relative importance, we show that measurement uncertainty is influenced by: available line parameter data, Dicke narrowing, line mixing, and collision-induced absorption effects.