Today we inspected the small NI viewport that was removed. During visual inspection of the ZnSe viewport after removal from the NI tower, a large number of reflective particulate-like features were observed on the optical surface exposed to the vacuum side while installed. The particles appeared as bright metallic/glitter-like flakes distributed across the central aperture and surrounding areas of the window. The distribution of the flakes was concentrated over a significant fraction of the clear aperture. Similar particulate debris was recovered from the surrounding handling surface. These observations are indicative of coating degradation and delamination from the ZnSe substrate (Figs. 1 and 2). Fig. 3 shows the air side of the viewport, which did not underwent the delamination process. The particles attached to this side seen on the photo are coming from the tissue that was contaminated from the vacuum side where the viewport was handled. 

The spare viewports that are going to be installed were also inspected by eye and both of them seems perfectly fine. Figs. 4 and 5 show both sides of the small viewport and Fig. 6 and 7 show both sides of the big viewport.