Stages of the data after progressive analysis steps, shown on the example of the third wavelength segment (2002.0–2014.6 nm) of night 5. Top to bottom: Data are shown as 1. the unnormalised time series; 2. after normalisation; 3. after masking of the deepest telluric lines (≤20% of the continuum level); 4. after nine SYSREM iterations. The lowest two panels show the same stage of analysis as the fourth; 5. with a CO₂ containing synthetic planet atmosphere injected at 200 times the strength expected for GJ 1214 b; and 6. with the masked regions set to zero (shown in yellow), to allow a visualisation of the amount of planet signal falling into the masked regions.