Total Hemispherical Emittance of Polyimide Films for Space Use in the Temperature Range from 173 to 700 K

This paper describes the temperature dependence of the total hemispherical emittance Eh in the temperature range from 173 to 700 K for three types of thermal control materials, which are based on a thin polyimide film coated with aluminum on the back surface. The results obtained from the measurements are compared with calculated values from optical constants. The principle of the present measurement is based on the steady-state calorimetric method, and Eh is obtained by measuring the equilibrium temperature of a sample corresponding to different heat inputs to a heater attached to the sample. On the other hand, the present calculation method is performed by using data for the optical constants of polyimide films and vapor-deposited metal in the wavelength region from 0.25 to 100 mm. These results agree with each other on the whole. It has been observed that the temperature dependence of Eh is remarkable, and the values have a maximum around 410 K.