Bottom panel: priors imposed on the length scale of the three squared exponential kernels used for the profile noise modeling. The labels μ and σ denote the mean and the standard deviation of each Gaussian distribution, respectively. The thick gray line is the sum of all three. Each of the top three panels shows three functions generated by each kernel and w values randomly drawn from the corresponding prior. The amplitudes were chosen so that they roughly match the typical variations in the RAVE spectra. The functions are separated by 0.05 in the vertical direction for clarity.