Top: posterior predictive distribution p(f(θ)|x_obs) of noiseless spectra (without the instrumental noise disturbance ϵ for the 99.7%. 95% and 68.7% quartiles (hues of blue), overlaid on top of the noiseless observed spectrum f (θ_obs), (black line). Bottom: residuals of the posterior predictive samples, normalized by the standard deviation of the noise distribution for each spectral channel.