Typical result of the retrieval procedure. This specific case is HD 209458 b with β = 15° and temperatures of 1800 and 1000 K on the dayside and nightside, respectively. Left panel: best-fit 1D spectrum (blue curve) along with the spectrum produced by our 3D tool used as input for the retrieval (black points with error bars being the 1σ uncertainty computed with PandExo). Right panel: posterior distribution for the retrieved parameters. This shows that the retrieval finds an acceptable fit, which results in relatively peaked posterior distribution and small error bars on the retrieved parameters. These values are however biased as the actual terminator temperature (1400 K) and atmospheric water abundance (log₁₀ [H₂O] = −1.3) are outside the range of values shown.