A phased approach to commissioning MCAO: Status and plans for the Linc-Nirvana Pathfinder


Al Conrad, Thomas Bertram, Martin Kürster, Tom Herbst, Roberto Ragazzoni, Jacopo Farinato, Valentina Viotto, Maria Bergomi, Alessandro Brunelli, Carmelo Arcidiacono, Jorg-Uwe Pott, Peter Bizenberger, Florian Briegel, Ralph Hofferbert, Wolfgang Gässler, Daniel Meschke, Lars Mohr, Ralf-Rainer Rohloff, Harald Baumeister, Fulvio De Bonis, Xianyu Zhang, Jan Trowitzsch, Jürgen Berwein, Frank Kittmann




Layer-oriented multi-conjugate adaptive optics (MCAO) systems apply two or more wavefront-sensor/deformable-mirror (WFS/DM) pairs, each conjugate to a different turbulent layer in the atmosphere. Because these pairs apply correction in series, they are largely decoupled from one another, lending them to a phased commissioning approach. Commissioning instruments on large telescopes, while almost always successful in the end, can be, experience has shown, inefficient and difficult to schedule. For Linc-Nirvana we plan to take advantage of the natural decoupling between the ground-layer subsystem (a 12-star pyramid WFS operating in conjunction with the LBT adaptive secondary) and the mid-high subsystem (an 8-star pyramid WFS working in conjunction with a Xynetics 349 actuator DM) to mitigate the difficulties that have been experienced commissioning complex instruments on large, over-subscribed, telescopes. Pathfinder is a test-bed, consisting of only those subsystems needed to operate, stand-alone, one of the two Linc-Nirvana ground-layer subsystems. The Pathfinder effort will tease out top-level interface issues; while at the same time providing a valuable characterization of the Mount Graham ground-layer. To what extent will this ground-layer system provide a seeing-corrected image to the next WFS/DM pair in the Linc-Nirvana system: the mid-high wavefront-sensor (MHWS)? We will present status and plans for the Linc-Nirvana Pathfinder effort, a novel approach for commissioning MCAO systems on large telescopes.

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