Black coatings essentially absorb incident light at all wavelengths from all directions. They are used when minimal reflection or maximum absorption is desired and therefore are effective in applications that require control of stray light. Our motivation stems from the use of black coating Lord Aeroglaze® Z302 in aerospace and remote sensing applications and the desire to support the development of bidirectional spectral models that can be used successfully to predict the performance of optical instruments such as telescopes. The bidirectional reflectance distribution function (BRDF) is an indispensable parameter in the optical characterization of such coatings. The current effort involves investigation of the BRDF of the commercial black coating Aeroglaze® Z302. An automated goniometer reflectometer has been designed, fabricated and successfully used for performing the BRDF measurements of Z302 at visible and ultraviolet wavelengths and at both polarizations. The current contribution involves study of Z302 samples prepared at different thicknesses and by different methods, which provides insight about influence of surface roughness on BRDF of Z302. / Master of Science / When light falls on different materials it undergoes various phenomenon such as reflection, refraction, absorption and scattering. The amount of each phenomenon varies with the optical nature of a material as well as the wavelength and direction of the light. Therefore, understanding the optical properties of materials at various wavelengths of light is necessary for effectively using those materialsin specific applications which require light to be efficiently reflected or absorbed. This research studies an optical property known as Bidirectional Reflectance Distribution Function (BRDF) of a black coating called Lord Aeroglaze Z302. Black coatings are materials that ideally absorb almost all light that falls on them irrespective of the light’s direction and wavelength. They are used in applications where maximum absorption of light is required. One such application which relates to the motivation for this research is absorbing unwanted light in instruments used in space such as telescopes and radiometers. Z302 is used in the Clouds and the Earth’s Radiant Energy System (CERES) instruments developed by NASA. BRDF is an important parameter which gives information about all other optical properties of a surface and can be used to know optical performance of that surface. The current work describes the experiments and an automated device developed, called reflectometer, to measure the BRDF of Z302 at different angles and wavelengths of light. The results are reported for different thickness samples of Z302 coating, and two different wavelengths of light that belong to the visible and ultraviolet spectrum of light.

The Thermal Radiation Group, a laboratory in the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University, is currently working to develop a new technology for thermal radiation detectors. The Group is also studying the viability of replacing current Earth Radiation Budget radiometers with this new concept. This next-generation detector consists of a thermopile linear array thermal radiation detector. The principal objective of this research is to develop an optical model for the detector and its cavity. The model based on the Monte-Carlo ray-trace (MCRT) method, permits parametric studies to optimize the design of the detector cavity and the specification of surface optical properties. The model is realized as a FORTRAN program which permits the calculation of quantities related to the cross-talk among pixels of the detector and radiation exchange among surfaces of the cavity. An important capability of the tool is that it provides estimates of the discrete Green's function that permits partial correction for optical cross-talk among pixels of the array. / Master of Science