Structural considerations for the Wide-Field/Planetary Camera II articulating fold mirror

The Articulating Fold Mirror (AFM) for the Wide Field/Planetary Camera-II (WF/PC-II) instrument is a very compact, complicated, highly precise mechanism. The AFM's basic function is to provide tip and tilt correction in the optical paths of the WF/PC-II instrument. Its necessity is brought about indirectly by the spherical aberration of the primary mirror in the Hubble Space Telescope (HST). Many challenges are created by the necessity of the new mechanism in the optical design. (1) The new mechanism must exhibit high precision in the placement of the mirror surface in two rotations (tip and tilt). (2) The available packaging volume for the AFM is very shallow and requires an innovative approach to achieve the necessary performance requirements. (3) The schedule for delivery of the flight certified AFM's is extremely tight, and as such does not allow for any failures during the qualification phase of the AFM project. Structural design and analysis plays a major role in meeting the stringent performance requirements within the schedule and fiscal constraints. The final result is a qualified mechanism which meets or surpasses all of its requirements.