CO(1–0) lines measured on June 12, 2009, plotted against synthetic lines computed assuming adjusted atmospheric models. Model 1 (for day and night conditions) corresponds to a model where only the temperature profile is adjusted, while the CO mixing profile is fixed to the reference profile. Model 2 (for day and night conditions) corresponds to a model where only the CO mixing profile is adjusted, while the temperature profile is fixed to the reference profile. Top: day-side spectra measured on the equator at 8′′ from the sub-earth point (9.3 am local time). Bottom: night-side spectra measured on the equator at 8′′ from the sub-earth point (3.1 am local time).