High performance shutter for space applications

A new concept of electromechanical shutter has been designed and qualified for the OSIRIS imaging system to fly onboard the Rosetta Mission, whose main scientific goal are the randez-vous and the study of the Comet Wirtanen. The shutter, is composed by two blades, driven by dedicated four-bar linkages, that are moved independently by two torque motors each mounted on the same shaft of an high resolution optical encoder. A dedicate fail safe mechanism is also integrated in order to make the shutter single point failure proof. The mechanism has been designed in order to fulfil high reliability with high performance. Reliability has been verified by life testing over 100000 cycles (factor 2 on expected operative cycles). Performance verified by calibration show that the minimum exposure time with a uniformity of 1/500 is 10 ms over a large sensitive area (about 30x30 mm). The exposure time can vary from 10ms to 5s. Scope of this paper is to present the mechanism and to demonstrate that it accomplishes the sciences and interfaces requirements.