The use of sodium laser guide star for Extremely Large Telescopes (ELT) adaptive optics systems is a key concern due to the perspective effect that produces elongated images in the Shack-Hartmann pattern. In order to assess the feasibility of using an elongated sodium beacon on an ELT, an on-sky experiment reproducing the extreme off-axis launch conditions of the European ELT is scheduled for summer and autumn 2016. The experiment will use the demonstrator CANARY installed on the William Herschel Telescope and the ESO transportable 20W CW fiber laser, embedded in the Wendelstein LGS unit. We will discuss here the challenges this experiment addresses as well as the details of its implementation and the derivation of the error budget.
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Lisa Bardou ; Eric Gendron ; Gérard Rousset ; Damien Gratadour ; Fabrice Vidal, et al.
Getting ready for the first on sky experiment using an ELT-scaled elongated sodium laser guide star
", Proc. SPIE 9909, Adaptive Optics Systems V, 990944 (July 27, 2016); doi:10.1117/12.2231611; http://dx.doi.org/10.1117/12.2231611