Abstract: Composition analysis of contaminant in thermal vacuum tests for spacecraft is the basis for the identification of the contaminant source and the effective control of contamination. The wiping method was used to collect deposits, which was then dissolved in acetone. The solution was analyzed by using GC/MS to identify and quantify the constituents of the contaminant. The contaminant found in a solar array thermal vacuum test was analyzed and it is shown to be methylphenylsilicone, which comes from adhesives for the solar cell. Residues of phthalates on satellite OSR and solar array surfaces were analyzed and quantified.