Apparatus to Measure Mid-Infrared Spectral Emittance of Cold Powers in a Vacuum

A compact apparatus enclosed in a stainless steel vacuum chamber was used to measure the 8–13 μ emittance of silicate powders under simulated lunar conditions for purposes of compositional analysis. Samples with surface temperatures as low as 180°K could be measured. The sample was contained in the removable lid of a constant temperature bath and its upper surface allowed to radiate into a cavity maintained at liquid nitrogen temperature (77°K). The spectral emittance was computed by matching the observed spectrum with a Planck function at high emittance wavelength intervals. System response was determined with an internal calibrating blackbody maintained at 273°K.