GLAO4ELT: a trade study and SAM experience

A. Tokovinin
It is expected that a substantial fraction of wave-front distortions at ELTs will be isoplanatic, being produced jointly by near-ground and dome turbulence, wind buffeting, flexures, and vibrations. We compare various strategies for sensing this ground component using (i) several sodium LGSs, (ii) one or several Rayleigh LGSs and (ii) NGSs in a wide field. The experience gained so far with the RLGS GLAO system SAM at 4-m telescope is presented. The results include wide-field...