ABSTRACT
Spacecraft payloads which operate at cryogenic temperatures often use passive thermal control systems that incorporate a variety of thermal control coatings to reject heat to space. The thermal performance of these systems depends significantly on the emittance of their thermal control coatings. This paper presents total hemispherical emittance measurements carried out at ISRO Satellite centre (ISAC) for thermal control coatings: Aeroglaze Z307 absorptive conductive polyurethane black coating (from 80K to 150K) and PUC conductive black polyurethane coating (from 70K to 200K). The experiments were conducted in vacuum using the steady state calorimetric method.
This paper highlights the importance of obtaining steady state for accurately estimating the emittance at cryogenic temperatures and the criterion for achieving this. The results indicate that the emittance in the cryogenic temperature range increases with temperature for the coatings considered in this paper. Determination of the uncertainty in the experimental results is also presented. Further, the sensitivity of emittance estimates to chamber wall emittance is discussed.
