Reliability oriented design and testing of a telescope's front cover for long life space mission

The reliability of a telescope's front cover for a space mission constitutes its primary demand, not to compromise the functionality of the whole instrument. From this point of view the design of the mechanism and the testing campaign should prove its fulfilment to the performance requirements, and its insensitivity to the environmental conditions, particularly for a long life mission where the performances have to be guaranteed along the whole lifetime of the experiment. The Front Door Mechanism (FDM) for the OSIRIS experiment of the ROSETTA mission has been developed and optimised minimising the loads transferred to the other components of the optical bench, and at the same time making it resistant to the loads of the launch and of the operating environment. The qualification and acceptance test campaigns conducted to demonstrate the compliance of the mechanism to the requirements, covered environmental tests such as vibration and thermal vacuum cycling, life test, resistant torque’s measurement and housekeeping sensor's reliability, and proved FDM’s reliability in terms of performances and insensitivity to the environmental conditions. The device showed also to be unaffected by the wear of the life test, keeping unaltered performances during the whole duration of the life test.