Primary Tweeters: Segmented Micro-Mirrors for Picometer-Scale Wavefront Compensation in Space-Based Observatories

Annbsp;objective for future decadal study missions is to detect exo-Earths usingnbsp;space-based telescopes with segmented primary mirrors (PMs). Wavefront control fornbsp;such telescopes will require small-stroke, high-precision deformable mirrorsnbsp;(DMs). The proposed innovation is a segmented microelectromechanical DM thatnbsp;can benbsp;used in NASA test beds as a surrogate for segmented PMs, or tonbsp;compensate wavefront errors of PM segments in future NASA programs. The projectnbsp;directlynbsp;addresses NASArsquo;s SBIR General Solicitation, Focus Area 10: Advancednbsp;Telescope Technologies, under the Science Mission Directorate Subtopic S2.01,nbsp;which callsnbsp;for a deformable source to simulate the telescope front end of anbsp;coronagraph undergoing deformations. In the proposed work, an objective is tonbsp;develop a DM havingnbsp;an array of hexagonal mirror segments, each supported by annbsp;array of underlying electrostatic actuators. Such a device could be used to activelynbsp;compensatenbsp;topographical errors in a PM. The proposed device has no hysteresisnbsp;and uses an all-silicon design that is intrinsically stable and insensitive tonbsp;environmentalnbsp;distortions.nbsp;The plan ofnbsp;worknbsp;builds on anbsp;successful Phase I project that demonstrated concept feasibility. It includes fabrication of DM segmentnbsp;arrays, use of annbsp;ion beamnbsp;figuringnbsp;process to planarize DMnbsp;mirror surfaces, and demonstration ofnbsp;active control ofnbsp;segment topography.nbsp;The outcome of this project will be a device that cannbsp;reduce telescope shape errors to lt;10nm RMS in NASA test beds usednbsp;fornbsp;development of future space-based observatories.