The wavelengths corresponding to the a refractive index of 1.2999 for ice at -40 C are 84.815, 1095, 8222, 12109, 30826, and 46423.5 nm.
Here is the problem though, recall that the angle of refraction is dependent upon the ratio of the refractive indices of the two optical materials. Using non-visible light means that the refractive index of air will also change (though not by much). What this means is that the angles will not match your diagram.
Going beyond visible wavelengths though stretches the idea beyond credibility. how would they detect infra-red radiation, or even microwaves for that matter? How would they even generate such rays? It is one thing to suggest that they had knowledge of refractive indices of air, and ice at -40 C for visible light, but another to suggest that they have knowledge of it at non-visible wavelengths. At least in principle, using visible light it is conceivable that they could have performed the experiments to obtain the correct angles, assuming they have a basic understanding of refraction.
This post was created using 100% recycled electrons