Results of environmental testing of the focus and alignment mechanism of the near-infrared camera on the James Webb Space Telescope

The Focus and Alignment Mechanism (FAM) is an opto-mechanical, cryogenic mechanism that positions the Pick-Off Mirror (POM) for the Near Infrared Camera of the James Webb Space Telescope. The POM is used to direct the light collected by the telescope into the Near Infrared Camera. The POM is a spherical, fused silica mirror. In order to retain high surface quality at cryogenic temperatures, the POM is attached to the mechanism via a titanium flexure-mount assembly. Three linear actuators are employed to position the POM in tip, tilt and piston. These linear actuators are stepper motor driven, with harmonic drive gear reduction. In this paper, we will summarize the design and role of this opto-mechanical mechanism and present the results of the environmental testing of the Engineering Test Unit. The tests performed were thermal-vacuum cryogenic cycling, and vibration testing.