Qualification of euclid-near infrared spectrophotometer cryomechanism

Already presented at 2015 ESMATS symposium [1], the CEA-Cryomechanism (CM) is a cryogenic rotating actuator that can operate from room temperature down to cryogenic environments, under vacuum or nitrogen atmosphere. In the framework of the Euclid-NISP space program, after having built two bread board model (BBM) units, CEA has undergone the integration of three qualification model (QM) units, among which one unit is going through a full qualification program (the two remaining units are intended to be qualified at upper system level). The cryomechanism was developed around 20 years ago and has a great heritage from ground based projects (VLT-VISIR). Originally, it included a combination of a stepper motor with a clutch system such as it was a discrete positioning actuator, providing high angular repeatability positioning capabilities (below 10 arcseconds peak to peak) for 360 stable positions a turn. For Euclid-NISP, the angular accuracy and repeatability specifications were widely relaxed after the CM preliminary design review. As consequence, the clutch system was removed from the CM design. After a short introduction for CM presentation, the paper will show the lessons learns from BBM campaign and the qualification campaign carried out on the qualification units. This tests campaign includes bearings characterization, motion profile measurements, angular repeatability measurements in representative environments (110K, under vacuum), vibrations tests at qualification levels, micro vibrations and exported forces/torques, dimensional controls, thermal cycles, electromagnetic tests, and life-test.