Well-established procedures for the characterization of contamination during outgassing usually involve total mass measurements through quartz crystal microbalance (QCM). Recently, the addition of mass spectrometry (MS) measurements to these data has become more common. The combination of both high sensitivity QCM and MS data may lead to a better understanding of the physics taking place during outgassing contamination processes. The way to do so is to complement the basic measurements of total mass loss on QCMs by the identification of each species and the quantitative determination of each species contribution.In a first characterization step, the thermogravimetric analysis of contaminants deposited on QCMs allows a partial species separation that helps exploiting mass spectrometry data. In return, these data permit a finer species separation. The key to these measurements is to obtain sufficient signal to noise ratio in the mass spectrometer. Though outgassing of space materials is not done the same way in Europe (multi-temperature steps, ECSS-Q-TM-70-52A) and in the US (isothermal, ASTM E-1559-09), both tests could be used to perform a first species separation, as reported here. Most species outgassed by a few common materials were identified (and quantified) through TGA and MS coupling. As reported in a companion paper, the knowledge of these species' spectra then allows the analysis of the MS data during the initial outgassing phase, determining the quantitative outgassing of each species and leading to the improved comprehension of the physical laws ruling outgassing.

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The prediction of contaminant levels is paramount to controlling and reducing their impact on space missions. In recent years, it has become clear that a real breakthrough could only be achieved through a change of paradigm, namely, by going beyond the classical characterization of total contaminant mass and instead characterizing the various emitted chemical species individually: both quantitatively and chemically. This paper first reviews the methodology proposed to achieve this objective and then its implementation on two examples of materials (Black Kapton® and NuSil CV4-2946) on the basis of existing ASTM-E-1559 outgassing data (Garrett, J. W., Glassford, P. M., and Steakley, J. M., “ASTM-E-1559 Method for Measuring Material Outgassing/Deposition Kinetics,” Journal of the IEST, Vol. 38, No. 1, 1995, pp. 19–28) including mass spectrometry (MS) data. We show that the thermogravimetric analysis performed on the contaminant deposits (heating at 1 K/min) allows a good enough time separation of chemical species to analyze and often identify them through their mass spectra. In turn, the knowledge of the fragments constituting their spectra allows an improved analysis of the MS data collected during the initial outgassing phase. The outgassing time profiles of each of these chemical species then tells a lot about their actual outgassing physical laws. On the two studied materials, outgassing physics were found to be consistent with Fickian or non-Fickian diffusion rather than with residence time desorption. After confirming these findings with more specific and more sensitive experiments, the door will be open to greatly improve assessments of the contaminant amounts and nature in flight through realistic multispecies physical models.

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