16 September 2015 Effect of DM actuator errors on the WFIRST/AFTA coronagraph contrast performance
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The WFIRST/AFTA 2.4 m space telescope currently under study includes a stellar coronagraph for the imaging and the spectral characterization of extrasolar planets. The coronagraph employs two sequential deformable mirrors (DMs) to compensate for phase and amplitude errors in creating dark holes. DMs are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Working with a low-order wavefront-sensor the DM that is conjugate to a pupil can also be used to correct low-order wavefront drift during a scientific observation. However, not all actuators in a DM have the same gain. When using such a DM in low-order wavefront sensing and control subsystem, the actuator gain calibration errors introduce highspatial frequency errors to the DM surface and thus worsen the contrast performance of the coronagraph. We have investigated the effects of actuator gain calibration errors and the actuator command digitization errors on the contrast performance of the coronagraph through modeling and simulations, and will present our results in this paper.
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Erkin Sidick, Erkin Sidick, Fang Shi, Fang Shi, "Effect of DM actuator errors on the WFIRST/AFTA coronagraph contrast performance", Proc. SPIE 9605, Techniques and Instrumentation for Detection of Exoplanets VII, 960506 (16 September 2015); doi: 10.1117/12.2188240; https://doi.org/10.1117/12.2188240

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