Emissivity measurement for low emissivity objects by two blackbody tube methods

Emissivity is not only an essential parameter for land surface temperature retrieval in remote sensing, but also a characteristic parameter to measure the ability of target´s thermal infrared radiation. Field measurement of emissivity is a challenging task, but one special feature is that it can obtain high accuracy of the emissivity. The Model 102 Portable Fourier Transform Infrared Spectrometer(Model 102FTIR spectrometer) [1] developed by Designs and Prototypes has less stray radiation, a wide spectral range, high resolution, however, it is very hard to measure the emissivity of objects with low emissivity such as aluminum. Two methods to measure the emissivity proposed by Zhang in 1985[2].In this paper, we use them based on the Model 102FTIR spectrometer and the blackbody tube to measure the low emissivity objects [2]. To evaluate the methods, marble, board, and aluminum are chosen as the samples which have respectively high, medium and low emissivity. Though the instant environment irradiance is changed, the real irradiance of the sample remains unchanged [3], the radiance temperature and emissivity separation algorithm are used to obtain the true emissivity curves of these samples. The emissivity curve of marble measured by the blackbody tube method matches very well with that measured by the instrument, which proves the feasibility of our methods. Meanwhile, low emissivity objects like aluminum meet the emission features in reality.