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Multilayer Insulation (MLI) is used for thermal control of spacecraft (S/C). Built-in discontinuities degrade the performance of MLI blankets. In this paper the blanket properties are considered by defining an effective emissivity for the MLI covered S/C surface. The influence of covered area and the influence of number of layers on the effective emissivity is determined by experiments with simple MLI covered test bodies in a space simulation chamber. An equation for the calculation of the effective emissivity of Soviet EVTI-type MLI is presented. The tests are combined with investigations of thermal similarity.

Function of satellite devices can considerably be affected by contamination. Contamination and secondary damages represent a complex problem. Several damages are possible, for example degradation of optical surfaces, which especially with unhindered solar radiation can lead to permanent change of optical parameters, or the change of thermo optical parameters of surfaces due to contminant layers, which perhaps can result in a considerable change of thermal balance of the device. In this special case a stringent requirement exists regarding surface cleanliness of a relatively large sensor target of Rhodium, which is an essential part of a chemical sensor being an element of the Cosmic Dust Analyzer (CDA) for the CASSINI-Mission. Especially contamination of heavy organics due to inadmissible outgassing from surrounding materials can spoil critical surface.