Intensity of the emergent radiation (left) and the PD (right) as functions of the cosine of the zenith angle. The atmosphere parameters are τ_T = 1.0, electron temperature T_e = 50 keV, and seed photon temperature T_bb = 1 keV. Black, blue, green, orange, and red solid lines show the model for photon energies of 2, 5, 8, 12, and 18 keV, respectively. The angular dependence of the intensity is normalized so that .