Advancing particle contamination monitoring in space applications: automated optical microscopy as an alternative approach

According to ECSS-Q-ST-70-50C, various direct and indirect methods exist for monitoring particle contamination, with Particle Fallout (PFO) meters being widely used. However, PFO meters have limitations, including a small measurement area and the ability to provide only information on the percentage of surface coverage. Alternative approaches, such as automated light microscopy for particle detection, have gained recognition as state-of-the-art techniques, despite not being explicitly covered in current ECSS standards. In this work, an advanced particle detection method utilizing automated transmitted light microscopy on glass substrates is presented. This approach offers a relatively large measurement area of approximately 5 cm² and delivers results within less than ten minutes. It provides detailed information on particle count (from single particles to several thousand), size (>2 µm), and morphology (e.g., round-shaped particles, fibers). These additional insights enhance contamination control strategies and contribute to improved cleanliness verification in space applications. Material analysis can be optionally performed using SEM. The developed technique represents a significant step toward more comprehensive and automated particle contamination assessment. Its integration into existing cleanliness protocols has the potential to improve monitoring efficacy and reliability in space-related AIT processes.