BiDirectional Reflectance Distribution (BRDF) of NASA Shuttle Tiles
Final rept. 2-18 Jan 1991
ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AFB TN
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Ground-based infrared IR cameras, located on a Maui mountaintop, are used to support a series of experiments associated with studying the condition of space shuttle tiles while in flight. This includes studying the reflective properties of the shuttle tiles while the shuttle is in orbit. Since the IR cameras used are sensitive in the 2.0- to 5.5-micron wavelength range the shuttle tile optical properties are required for the same spectral range. The optical property of particular interest is the tile Bidirectional Reflectance Distribution Function BRDF. The tile BRDF is input into radiation models to help predict the expected power levels observed by the IR cameras. The objective of the tests reported was to measure the tile BRDF over the range of 2.0- to 5. 5-micron as a function of reflectance angle. The BRDF of both black and white flown and un-flown shuttle tiles were measured. This report describes the apparatus and method used to measure the BRDF of both black and white, flown and unflown, NASA space shuttle tiles. Measured data are included in the report appendix.