29 July 2016 Low order wavefront sensing and control for WFIRST coronagraph
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Abstract
To maintain the required WFIRST Coronagraph starlight suppression performance in a realistic space environment, a low order wavefront sensing and control (LOWFS/C) subsystem is necessary. The LOWFS/C uses the rejected stellar light from coronagraph to sense and suppress the telescope pointing drift and jitter as well as the low order wavefront errors due to changes in thermal loading on the telescope and the rest of the observatory. In this paper we will present an overview of the low order wavefront sensing and control subsystem for the WFIRST Coronagraph and describe the WFIRST Coronagraph LOWFS function, its design, and modeled performance. We will present experimental results on a dedicated LOWFS/C testbed that show that the LOWFS/C subsystem not only can sense pointing errors better than 0.2 mas but has also experimentally demonstrated closed loop pointing error suppression with residuals better than 0.4 mas rms per axis for the vast majority of observatory reaction wheel speeds.
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Fang Shi, Kunjithapatham Balasubramanian, Randall Bartos, Randall Hein, Raymond Lam, Milan Mandic, Douglas Moore, James Moore, Keith Patterson, Ilya Poberezhskiy, Joel Shields, Erkin Sidick, Hong Tang, Tuan Truong, James K. Wallace, Xu Wang, Daniel W. Wilson, "Low order wavefront sensing and control for WFIRST coronagraph", Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 990418 (29 July 2016); doi: 10.1117/12.2234226; https://doi.org/10.1117/12.2234226
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