Using the vector vortex coronagraph in the ExAO regime at Palomar: lessons learned


D. Mawet, E. Serabyn, R. Burruss


JPL - Caltech


We have been using the vector vortex coronagraph intensively on sky behind the 1.5-meter well-corrected subaperture on the 5-m Hale telescope at the Palomar observatory. This configuration allowed us to experiment the use of this small inner working angle, high throughput, clear and symmetric off-axis discovery space coronagraph in the ExAO regime. We will discuss the system level issues we had to tackle to make the most of this instrumental setup: low-frequency and high frequency pointing stabilization, focus removal, non-common path wavefront errors calibrations using the modified Gerchberg-Saxton phase retrieval technique, synchronized observing strategy. Without the availability of differential imaging capabilities such as angular or spectral differential imaging, we had to rely on the well-proven reference star subtraction. While not ideal, this method will be the only way to get to close separations since both ADI and SDI fail at very small angles. Fast and reproducible AO target acquisition allowed us to implement an efficient target-reference nodding method which is the key to achieving a high degree of correlation in the quasi-static speckle pattern required by smart data processing methods such as the locally optimized combination of images (LOCI).

Attached documents

Lyot2010proc s8 talk MawetD.pdf
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