Simulated spectral radiance at the top of the atmosphere for Proxima Centauri b in (a) 1:1 SOR and (b) 3:2 SOR, for θ(t) as shown in Table 1. The spectra were created using PSG and the GlobES tool (see Sect. 2.2 for details). We also include blackbody curves at different temperatures for comparison and grey rectangles for important molecular and CIA features. For panel (b), the solid and dashed lines represent the first and second orbits around the host star, respectively, and together correspond to the length of a full day for the 3:2 SOR.