22 August 2014 Realtime speckle sensing and suppression with project 1640 at Palomar
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Abstract
Palomar’s Project 1640 (P1640) is the first stellar coronagraph to regularly use active coronagraphic wavefront control (CWFC). For this it has a hierarchy of offset wavefront sensors (WFS), the most important of which is the higher-order WFS (called CAL), which tracks quasi-static modes between 2-35 cycles-per-aperture. The wavefront is measured in the coronagraph at 0.01 Hz rates, providing slope targets to the upstream Palm 3000 adaptive optics (AO) system. The CWFC handles all non-common path distortions up to the coronagraphic focal plane mask, but does not sense second order modes between the WFSs and the science integral field unit (IFU); these modes determine the system’s current limit. We have two CWFC operating modes: (1) P-mode, where we only control phases, generating double-sided darkholes by correcting to the largest controllable spatial frequencies, and (2) E-mode, where we can control amplitudes and phases, generating single-sided dark-holes in specified regions-of-interest. We describe the performance and limitations of both these modes, and discuss the improvements we are considering going forward.
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Gautam Vasisht, Gautam Vasisht, Eric Cady, Eric Cady, Chengxing Zhai, Chengxing Zhai, Thomas Lockhart, Thomas Lockhart, Ben Oppenheimer, Ben Oppenheimer, } "Realtime speckle sensing and suppression with project 1640 at Palomar", Proc. SPIE 9148, Adaptive Optics Systems IV, 914822 (22 August 2014); doi: 10.1117/12.2056591; https://doi.org/10.1117/12.2056591
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