Hemispherical emissivity ɛ_h(w_n, a) of regolith grains with various sizes a. (top) 10 µm, (middle) 100 µm, (bottom) 1 mm, and various types of mixing: no contaminants (Ih90), with 5% AmC (black) or 1% Th (red) either mixed at intra-particle scale (dotted line), or with aerial (dashed line) or volumic (dash-dotted line) mixing. esa diffraction correction is assumed. Left: 10–700 cm⁻¹ range and right: 5–14.3 µm range (700–2000 cm⁻¹).