A knowledge of the emissivity of a cavity radiator may be deduced from reflectance measurements, but these may be difficult to make if the cavity has a small aperture and low reflectance. The use of a He-Ne laser as a source facilitates such measurements. Results are presented for one ceramic and three metallic cavities that have been used in photometric and spectroradoimetric standards work. An integrating sphere method appears more satisfactory than a goniophotometric approach.
O. C. Jones and C. Forno, "Reflectance Measurements on Cavity Radiators," Appl. Opt. 10, 2644-2650 (1971)