The Mode Selector Mechanism (MSM) is a bi-stable cryo-actuator operated at 4.2 K developed by Centre Spatial de Liège. The MSM development started as part of the far -infrared spectrometer SAFARI on the ESA SPICA space telescope. It takes place now in the preparation and anticipation of next generation cryogenic missions.
The MSM is characterized by its ability to switch an optical part such as a mirror between two defined positions at ambient as well as at cryogenic temperature. The particularit y of this bi-stable actuator is the capacity to ensure a passive locking, in order to eliminate electromagnetic interference sources. The actuator is also optimized regarding the energy dissipated during actuation. For that reason, specific elements such as ultra-thin magnets and metallic additive manufactured parts are included in the actuator.
In this talk, we present key aspects of the thermal design and the driving parameters to get an actuation at 4.2 K. The thermal demonstrator models in preparation will be presented as well to better know the properties of the key items thermally dependent (coil wire resistivity, pivots springs torque, thin magnets remanence). This includes the design of the cryostat, the measurement method at 4.2 K, and the status of the breadboard activities with first results.