The objective of this thesis was 1) to study the radiative properties of silicon in the wavelength range of 1 to 20 microns and temperature range of 30 to 1000°C for the development of a multi-wavelength pyrometer 2) to develop a [sic] methodologies for deconvolution of the measured optical properties to yield fundamental optical constants of bulk materials. A novel spectral emissometer has been utilized for measurement of the temperature dependent radiative properties of silicon. The temperature determination capability of the emissometer was tested and verified using a standard thermocouple embedded in a silicon wafer. The temperature measurement accuracy, with the emissometer, was found to be within ± 10°C of the thermocouple temperature for a temperature range of 30 to 300°C. The experimental results presented in this thesis showed that the measurement of high temperature optical properties could be performed reliably with a novel non-contact, real-time approach using the spectral emissometer. The optical properties of n and p-type lightly and heavily doped silicon wafers were investigated. These studies have led us to establish spectral emissometer as a reliable technique for simultaneous measurements of radiative properties and temperature in the 1-20 µm wavelength range.