Strain gauging for on-orbit figure monitoring of adjustable X-ray optics: systems analyses

Adjustable X-ray optics represent a potential mirror technology for the NASA Lynx X-ray observatory mission concept. Adjustable optics employ an integrated micron-thick piezoelectric film deposited on the convex side of silicon Wolter-type mirror segments. Discrete, independently addressable electrodes on the convex surface form individual actuators; the applied voltages are used to correct the shape of the mirror segments for figure errors resulting from a change in thermal environment, epoxy creep, or failure of an epoxy bond. On-orbit correction requires a metrology system to provide real-time feedback of mirror figure. We are examining the use of deposited semiconductor strain gauges to monitor mirror mechanical strains and surface temperatures. To establish requirements for monitoring we modeled a variety of thermal and mechanical disturbances to a mirror segment such as might occur on-orbit or from launch. Models are described and resulting requirements and performance discussed.