An objective for future decadal study missions is to detect exo-Earths using space-based telescopes with segmented primary mirrors (PMs). Wavefront control for such telescopes will require small-stroke, high-precision deformable mirrors (DMs). The proposed innovation is a segmented microelectromechanical DM that can be used in NASA test beds as a surrogate for segmented PMs, or to compensate wavefront errors of PM segments in future NASA programs. The project directly addresses NASA’s SBIR General Solicitation, Focus Area 10: Advanced Telescope Technologies, under the Science Mission Directorate Subtopic S2.01, which calls for a deformable source to simulate the telescope front end of a coronagraph undergoing deformations. In the proposed work, an objective is to develop a DM having an array of hexagonal mirror segments, each supported by an array of underlying electrostatic actuators. Such a device could be used to actively compensate topographical errors in a PM. The proposed device has no hysteresis and uses an all-silicon design that is intrinsically stable and insensitive to environmental distortions. The plan of work builds on a successful Phase I project that demonstrated concept feasibility. It includes fabrication of DM segment arrays, use of an ion beam figuring process to planarize DM mirror surfaces, and demonstration of active control of segment topography. The outcome of this project will be a device that can reduce telescope shape errors to <10nm RMS in NASA test beds used for development of future space-based observatories.
Segmented deformable mirrors that are suitable for correcting surface figure error and stability in primary telescope segments and serving as a primary mirror array surrogates in telescope testbeds have a few NASA applications. The following application applies to DMs designed for this program.
Space-based astronomical telescopes: A number of missions require the control provided by the proposed DMs such as LUVOIR and HabEx. These devices will fill a critical technology gap in NASA’s vision for high-contrast imaging and spectroscopy instruments.
Deformable mirrors suitable for correcting surface figure error and stability in primary telescope segments and as primary mirror surrogates in telescope testbeds have non-NASA applications. They can improve the performance of terrestrial telescopes such as TMT and E-ELT. Surrogate devices can be used in testbeds to develop instruments for telescopes with segmented primary mirrors.