Integrating-sphere-free reflectometry of blackbody cavity emissivity using the ratio of hemispherical–given solid angle reflections

Blackbody cavity reflectivity is normally measured using an integrating sphere to collect hemispherical reflected radiation from a blackbody opening when illuminated by a directional light source. The challenge of taking this method without an integrating sphere arises for blackbody cavity emissivity measurement in satellites due to space constraints. The ratio of hemispherical–given solid angle reflections is proposed to calculate the total reflected power from a blackbody cavity by multiplying a measurable reflected power in a given solid angle. The ratio is obtained by simulating the distribution relationship between the total hemispherical reflected light power and the reflected light power in the given solid angle under different coating emissivity. The emissivity measurement results are consistent with radiometric method measurements and simulation results, with an uncertainty of 0.0005.