A Multi-angle Reflectance Measurement System And Its Calibrations

Remote sensing in the visible wavelengths plays a key role in retrievals of the geological information on planetary surfaces such as mineral compositions and rego-lith physical properties. The bi-directional reflectance distribution function (BRDF) is an important parameter that describes how a surface scatters light into different direc-tions when illuminated from different directions. The accurate knowledge of the BRDF of a planetary surface is not only needed in calibrations of remote sensing data measured under different configurations, but also crucial in the inversions remote sensing data to retrieve the chemical and mineral compositions of the surface. For example, the particle size distributions of the lunar surface may be estimated from the phase curve which is essentially the BRDF. BRDF is also extensively used in other fields such as remote sensing of the Earth, mechanical engineering and computer graphics. Therefore, constructions of laboratory devices capable of measuring differ-ent surface BRDF would be of great interest to these research areas. In this thesis, an instrumentation design including the 3D and 2D computer-aided mechanical design, circuits descriptions, optical system and control software are presented. The system can perform automated data acquisition thanks to a computer controlled servo motor and the control software written in C++. By using a monitor channel to reduce laser power fluctuations, the measured signal can achieve a stability better than ～0.5%. Preliminary measurements on shallow water sediments, lunar soil stimulant and Mar-tian soil simulant, show that the data have good quality and can be used in quantita-tive studies of geological samples. As an application example, I also present our phase curve analysis of the Chang’E-3 in-situ lunar data to show the importance of the BRDF study.