29 July 2016 High-contrast imager for Complex Aperture Telescopes (HiCAT). 4. Status and wavefront control development
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Abstract
Segmented telescopes are a possible approach to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the increased complexity of their aperture geometry, due to their central obstruction, support structures and segment gaps, makes high-contrast imaging very challenging. The High-contrast imager for Complex Aperture Telescopes (HiCAT) was designed to study and develop solutions for such telescope pupils using wavefront control and starlight suppression. The testbed design has the flexibility to enable studies with increasing complexity for telescope aperture geometries starting with off-axis telescopes, then on-axis telescopes with central obstruction and support structures (e.g. the Wide Field Infrared Survey Telescope [WFIRST]), up to on-axis segmented telescopes e.g. including various concepts for a Large UV, Optical, IR telescope (LUVOIR), such as the High Definition Space Telescope (HDST). We completed optical alignment in the summer of 2014 and a first deformable mirror was successfully integrated in the testbed, with a total wavefront error of 13nm RMS over a 18mm diameter circular pupil in open loop. HiCAT will also be provided with a segmented mirror conjugated with a shaped pupil representing the HDST configuration, to directly study wavefront control in the presence of segment gaps, central obstruction and spider. We recently applied a focal plane wavefront control method combined with a classical Lyot coronagraph on HiCAT, and we found limitations on contrast performance due to vibration effect. In this communication, we analyze this instability and study its impact on the performance of wavefront control algorithms. We present our Speckle Nulling code to control and correct for wavefront errors both in simulation mode and on testbed mode. This routine is first tested in simulation mode without instability to validate our code. We then add simulated vibrations to study the degradation of contrast performance in the presence of these effects.
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Lucie Leboulleux, Lucie Leboulleux, Mamadou N'Diaye, Mamadou N'Diaye, A. J. Eldorado Riggs, A. J. Eldorado Riggs, Sylvain Egron, Sylvain Egron, Johan Mazoyer, Johan Mazoyer, Laurent Pueyo, Laurent Pueyo, Elodie Choquet, Elodie Choquet, Marshall D. Perrin, Marshall D. Perrin, Jeremy Kasdin, Jeremy Kasdin, Jean-François Sauvage, Jean-François Sauvage, Thierry Fusco, Thierry Fusco, Rémi Soummer, Rémi Soummer, } "High-contrast imager for Complex Aperture Telescopes (HiCAT). 4. Status and wavefront control development", Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99043C (29 July 2016); doi: 10.1117/12.2233640; https://doi.org/10.1117/12.2233640
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