28 August 2014 Experimental study of a low-order wavefront sensor for high-contrast coronagraphic imagers: results in air and in vacuum
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For the technology development of the mission EXCEDE (EXoplanetary Circumstellar Environments and Disk Explorer)—a 0.7 m telescope equipped with a Phase-Induced Amplitude Apodization Coronagraph (PIAA- C) and a 2000-element MEMS deformable mirror, capable of raw contrasts of 10−6 at 1.2 λ/D and 10−7 above 2 λ /D — we developed two test benches simulating its key components, one in air, the other in vacuum. To achieve this level of contrast, one of the main goals is to remove low-order aberrations, using a Low-Order WaveFront Sensor (LOWFS). We tested this key component, together with the coronagraph and the wavefront control, in air at NASA Ames Research Center and in vacuum at Lockheed Martin. The LOWFS, controlling tip/tilt modes in real time at 1 kHz, allowed us to reduce the disturbances in air to 10−3 λ/D rms, letting us achieve a contrast of 2.8×10−7 between 1.2 and 2 λ/D. Tests are currently being performed to achieve the same or a better level of correction in vacuum. With those results, and by comparing them to simulations, we are able to deduce its performances on different coronagraphs— different sizes of telescopes, inner working angles, contrasts, etc. — and therefore study its contribution beyond EXCEDE.
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Julien Lozi, Julien Lozi, Ruslan Belikov, Ruslan Belikov, Sandrine J. Thomas, Sandrine J. Thomas, Eugene Pluzhnik, Eugene Pluzhnik, Eduardo Bendek, Eduardo Bendek, Olivier Guyon, Olivier Guyon, Glenn Schneider, Glenn Schneider, } "Experimental study of a low-order wavefront sensor for high-contrast coronagraphic imagers: results in air and in vacuum", Proc. SPIE 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 914322 (28 August 2014); doi: 10.1117/12.2056735; https://doi.org/10.1117/12.2056735


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