Absorbing coatings and diffuse reflectors for the Herschel platform sub-millimeter spectrometers HIFI and PACS

Abstract

Absorbing coatings for the HIFI and PACS spectrometers aboard the Herschel platform have been developed and optically characterized. Using radiation from an optically pumped far-infrared laser at wavelengths in the 90-900 /spl mu/m range, the specular as well as the diffuse reflection - described by the bi-directional reflection distribution function - have been determined. The influence of polarization has been addressed too. Moreover, the absorption of non-absorbing diffusely reflecting surfaces, to be used for integrating spheres, has been determined using a calorimetric method.