Future advanced telescopes require active mirror compensation without the complexity of real-time adaptive control. Current wavefront correctors, while dimensionally stable, require closed loop control using a wavefront sensor and complicated electronics to maintain mirror shape. For space based systems, simplified open loop control is desirable since it reduces power and weight while greatly improving system reliability by reducing complexity and electronic parts count. Xinetics proposes a Programmable Relaxor Open-Loop Mirror using Integrated Spatial Encoders (PROMISE) that combines surface parallel actuation and micro optical encoders. The programmable relaxor open-loop mirror uses a surface parallel actuator array, made using ferroelectric micromachining originally developed for silicon based MEMS. The programmable actuator array enables the dimensionally stability and angstrom level control provided only by relaxor ferroelectrics, as has been demonstrated by the Jet Propulsion Laboratory. The integrated spatial encoder features an optical encoder that monitors dimensional change and is integrated directly between the actuator array and the surface mount interconnect. The voltage output of the optical encoder is used as a direct input to the feedback loop for the actuator circuit enabling electroactive control of the mirror surface without the necessity of an optical sensor, thereby enabling open loop control.
