Results Of A CO2 BRDF Round Robin

ABSTRACT The results of a nationwide CO2 BRDF round robin are presented. This study was conducted as a follow -on to a 1988 0.6328 ,um BRDF round robin.t1 Four master samples ranging in roughness from a diffuse surface to a 45 A rmsmirror were measured at six scatter facilities. BRDF data in the forward direction for an incidence angle of 10 ° is compared from all participating facilities for the four samples. Unfortunately, the samples were lost during shipmentbetween scatter facilities, and it was not possible to complete measurements at the 14 planned facilities.1. INTRODUCTIONA previous BRDF round robin conducted in 1988 at 0.6328 pm showed the need for confirmation of BRDFmeasurements to assure accuracy. Infrared radiometry holds more subtle pitfalls than visible radiometry, so this roundrobin was conducted to assess level of confidence in CO2 laser BRDF measurements. The master sample set consisted of four, two -inch diameter samples. WH - diffuse white surface with THR =0.70 (experimental lambertian from a commerical vendor).BL - diffuse black surface made by sandblasting, etching and anodizing aluminum.BE - polished Beryllium mirror, 90 A rms.MO - polished Molybdenum mirror(M14) used in 0.6328 µm round robin, 45 A rms.Unfortunately, the sample case was lost by Federal Express after measurements were made at six facilities. Two ofthe facilities also spun the diffuse samples for a total of eight measurement sets for the diffuse samples. This providedsufficient data to make comparisons, draw conclusions about some of the error sources and make recommendations to