Reflectance measurements on submillimeter absorbing coatings for HIFI

Specular and diffuse reflectance (BRDF) of black absorbing coatings, meant to be used for the HIFI instrument aboard the FIRST satellite, has been studied in the sub-millimeter region (0.1 -2 Sr -1 throughout the wavelength range of interest, quite independent of directions of incidence, reflection and polarization. The Total Hemispherical Reflection of such a coating will then be 0.06.