Design and testing of a roto-translational shutter mechanism for planetary operation

• An innovative roto-translational mechanism was designed to provide sealing of a miniaturized interferometer against dust deposition and external contamination.
• Mechanism mass was limited to 30 g and the expected working thermal range was extended down to −80 °C.
• Multibody model was developed to investigate sensitivity about friction conditions during the motion phases.
• Mechanism mockup was made and successfully tested within expected mechanical and thermal environments.

This work describes the design and testing of a shutter mechanism for a miniaturized infrared spectrometer developed for the ESA ExoMars Pasteur mission. Unlike most usual cover mechanisms, the conceived one provides a roto-translational motion. This feature allows the sealing of the interferometer main entrance window from dust contamination, in addition to the usual function of shuttering the instrument field of view. Although this characteristic is strongly desired because it avoids dust deposition and optics contamination while the instrument is not operating, it makes the mechanism design significantly more complex. Moreover, challenging design constraints were faced: the mass budget allowed for no more than 30 g allocation, the expected working thermal range extended down to −80 °C and high vibration levels with an acceleration peak of 670 m/s2 were predicted during Mars landing. To complete the picture, the mechanism cover was required to provide also a calibration target for the 2–25 μm spectral range of the spectrometer. The resulting system is made by a calibrating/shutter cover moved by a purposely designed out of plane cams system which provides the desired motion. A mechanism mockup was assembled and successfully tested in the predicted thermal and mechanical environments.