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Proceedings Paper

Compensating for pupil rotation in the W.M. Keck Observatory adaptive optics system
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Paper Abstract

The non-circular shape of the Keck telescopes primary mirror, combined with the fact that the telescope is on an alt/az mount with the adaptive optics system on the left Nasmyth platform, means that as the telescope tracks a star field the hexagonal pupil image rotates on the wavefront sensor camera and on the deformable mirror. This creates a need for a dynamic control strategy. The control matrix, the list of which subapertures are sufficiently illuminated and the list of which actuators are active and which are slaved, all must change on the fly, with the loops closed and without perturbing a science observation in progress. This control strategy must also be robust in the presence of modest pupil translation. These needs are met in the Keck AO system by the Pupil Rotation Compensation (PRC) software tool. The PRC software is responsible for maintaining system parameters that are functions of the pupil position and orientation. This paper will present the details of the PRC software design including algorithms used for selecting active subapertures, dealing with variable subaperture illumination, calculating control matrices, and slaving actuators outside the pupil illuminated area on the deformable mirror.

Paper Details

Date Published: 7 July 2000
PDF: 12 pages
Proc. SPIE 4007, Adaptive Optical Systems Technology, (7 July 2000);
Show Author Affiliations
Paul J. Stomski Jr., W.M. Keck Observatory (United States)
J. C. Shelton, Carpe Photon (United States)

Published in SPIE Proceedings Vol. 4007:
Adaptive Optical Systems Technology
Peter L. Wizinowich, Editor(s)

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