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Published May 2011 | public
Journal Article

Minimum Variance Split Tomography for Laser Guide Star Adaptive Optics

Abstract

Tomographic wavefront estimation using laser and natural guide stars is under development for ground-based extremely large telescopes. Typical wavefront sensing requirements include several bright mesospheric sodium laser guide stars (LGSs) supplemented byafew dim natural guide stars (NGSs) required to sense at low frame rateasmall number of low-order atmospheric modes poorly measured by the LGS wavefront sensors (WFSs). A conditional mean formulation of minimum variance wavefront estimation is given in this context to split the LGS and NGS components of the estimation in suchaway that the LGS component does not depend upon the NGS asterism (location and brightness). This split formulation is analytically equivalent to the standard (integrated) formulation of minimum variance wavefront estimation and is therefore optimal and fully applicable to all laser tomography systems (multi conjugate and multi object). Temporal blending for closed loop feedback systems is discussed, and detailed multi-rate Monte Carlo simulations of the Thirty Meter Telescope (TMT) multi conjugate adaptive optics (MCAO) system are presented, demonstrating the potential of minimum variance split tomography compared toasimpler ad hoc split developedadecade ago for the MCAO system of the Gemini South telescope.

Additional Information

© 2011 EUCA. Received January 29, 2010; Accepted Septemher 30 2010. The authors acknowledge stimulating discussions with Jean-Pierre Veran and Glen Herriot from the Herzberg Institute of Astronomy, Canada, regarding the temporal blending issues. The authors gratefully acknowledge the support of the TMT partner institutions. They are the Association of Canadian Universities for Research in Astronomy (ACURA), the California Institute of Technology and the University of California. This work was supported as well by the Gordon and Betty Moore Foundation, the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the National Research Council of Canada, the Natural Sciences and Engineering Research Council of Canada, the British Columbia Knowledge Development Fund, the Association of Universities for Research in Astronomy (AURA) and the U.S. National Science Foundation.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023