viewports

​​​​Two big viewports

The main and biggest viewport with an optical diameter of 139mm is made of Magnesiumfluoride (MgF2) for wavelength up to 6µm in the infrared. With its low refraction index, it does not need an anti-reflection coating. It was ordered at Torr Scientific Ltd.

The second viewport is made of borosilicate glass with a diameter of 136mm and is placed opposite. This is used for example to simulate the sunlight from behind, used for a mission like CHEOPS, or simply for alignment purposes.

The two big flanges improve the mechanical stability of the vacuum chamber and allow mounting a plate with several different viewports if necessary, for e.g. one for the Laser of a LIDAR or other smaller flanges to be flexible.

The viewports are mounted parallel and not tilted into the flanges. To prevent ghost images the optical line must be tilted some degrees.