Vacuum conditions, outgassing of test article's materials and desorbing gas loads from spacecraft or test facility during thermal testing can have an essential impact on thermal balance conditions, potential contamination processes and functional performance of specific spacecraft components or experiments. For the medium size (approximate to 50 m(3) volume) and the large thermal testing facility (approximate to 500 m(3) volume) of IABG measurements of the gassing rate have been performed for dry runs and for satellite thermal tests. By pressure rise measurements the gassing rate for the facilities and their time dependence were determined. The data show that the processes include diffusion and desorption processes, and indicate a leak rate determination method. In addition to gassing rates and their impact on optimization of the pumpdown procedure and of the available He refrigerator cryopump pumping capacity the desorption and outgassing from in ner spacecraft surfaces and the resulting inner volume pressure are important with respect to functional performance of spacecraft experiments and components. [References: 10]
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