Calibrated Moon radiances for the 19 HIRS thermal IR filters for all 22 observing epochs, as a function of phase angle. The data at the top (diamonds) are from the long-wavelength channels 1–12 (14.9–6.7 μm). The lower data points (triangles) are from the short-wavelength channels 13–19 (4.6–3.7 μm). The variation in radiance at a given phase angle is mainly related to the different wavelengths (from below 4 μm to almost 15 μm) and heliocentric distances of the Moon (ranging from r = 0.985 to 1.018 au).