PRECISE EMISSIVITY OF ROCK SAMPLES

To differentiate among geological materials and vegetation using therm al infrared spectra, radiometric measurements require corrections for focal temperature variations and reflected radiation. A laboratory tec hnique is described for the determination of spectral emissivity signa tures for natural geological samples using a Fourier Transform Infrare d Spectrometer and the self-emission of the scene. The approach descri bed does not require control of the sample temperature. A quantitative assessment of uncertainties is presented. Comparison of the emissivit y measurements from natural geological specimens with hemispherical re flectance data gave an average difference of about 0.01 in emissivity, except near strong features of the spectra. The technique is applicab le to field measurements of high-emissivity objects.