Design and characterisation of black-body sources for infrared wide-band Fourier transform spectroscopy

The design and characterisation of small and cost-effective reference black-bodysources for radiometric calibration of Fourier transform spectrometers in the midand far infrared is presented. The paper describes the optimisation of the absorbingblack-coating material and the study of two types of cavity geometry, one designedfor collimated beams and one for focused beams. These two reference sources havebeen developed for the Radiation Explorer in the Far InfraRed spectrometer cov-ering the 100-1400 cm −1 spectral range. They are currently used on-board twoprototypes for ground and stratospheric balloon based atmospheric emission mea-surements. An emissivity of better than 0.9999 is obtained for both type of cavitygeometry giving a calibration error, depending only on the temperature gradientinside the blackbody, of less than 0.5 K. Keywords: Fourier transform spectra, Infrared spectroscopy, Blackbody radiation PACS: 33.20.Ea, 07.57.Ty, 44.40.+a 1 IntroductionIn emission spectroscopy, the calibration of the observed radiance requiresthe measurement of a known source of radiation, which typically is givenby the emission of a blackbody (BB) cavity described by the Planck law ofradiation. The design of a well-characterised and reliable BB source can be