Experimental measurements of thermal radiation properties by cyclic incident radiation.

A new experimental technique is developed to determine simultaneously the total hemispherical emittance, solar absorptance, and absorptance-emittance ratio for metals at cryogenic temperatures. The method compares the temperature response of thin metal samples to a sinusoidal perturbation of an imposed radiant intensity. Emittance data are presented for aluminum, copper, and 304 stainless steel over the temperature range 150-500 K. From the data, the applicability of the cyclic radiant intensity method is evaluated, and the problems associated with extending the method to temperatures below 150 K are discussed.