Notes. The simulation was done for a single dust SED typical of the 10% faintest area of the sky, whose parameters are the median values found in the low N_{H i} mask: T_obs = 20.8 K, β_obs = 1.55 and τ₃₅₃ = 9.6 × 10^-7 (Table 3). The CIBA was modelled assuming partial correlation in frequency (see Appendix C for details). The noise and CIBA levels used for each resolution are given in Table C.1. The values given here are the standard deviations of the parameters T_obs and β_obs obtained from three-parameter SED fits of 10⁵ realizations; δ_noise and δ_CIBA represent the separate contributions of noise and the CIBA to the total standard deviation.