The remote measurement of the emissivity of ground materials is of tremendous value in their identification and mapping. Traditional techniques use reflected solar radiation for this measurement for wavelengths shorter than 5 micrometers . With the development of new techniques, the 10 micrometers atmospheric transmission window might also be used for this purpose. Previous work using the multiangle data acquisition technique demonstrated its utility to determine source thermal emission. Here we find the multiangle technique can be used to determine the source specular reflectivity to approximately 0.05 if there is very good system performance.
John R. Henderson,
"Remote measurement of ground source emissivity", Proc. SPIE 2553, Infrared Spaceborne Remote Sensing III, (29 September 1995); doi: 10.1117/12.221383; https://doi.org/10.1117/12.221383