During the qualification campaign of the NIRSpec (near-infrared spectrometer) instrument mechanism, the actuator could not achieve the expected lifetime that had been extended during the development phase. The initial design could not be adapted to the requested number of revolutions during that phase. Consequently the actuator needed to be modified so that the function of the mechanism would not be
endangered or, by extension, the overall function of the NIRSpec instrument. The modification included a
change of the overall actuator design—internal dimensions, tolerances, materials, lubrication and assembly
process—while keeping the interface to the mechanism, mass and function.
