Variation of Thermal Emittance of Thermal Control Materials during Simultaneous Irradiation of Electrons and Ultraviolet Rays

Variation of the total hemispherical emittance of spacecraft thermal control films resulting from irradiation is discussed. An electron energy of 30 KeV and a UV intensity of 3 sun equivalents are used. The emittance is measured in situ by the calorimetric method. The emittance of silver-Teflon film increases slightly with increasing the electron fluence. Its increment is less than 0.02 at a fluence of 1 × 10¹⁵ e/cm², and very small for further irradiation. Addition of UV rays does not alter this situation. The emittance of aluminized Kapton film is not changed appreciably by irradiation.