Laboratory demonstrations of LTAO on 30-m telescopes at visible wavelengths: Including multiple natural guide stars
S. Mark Ammons, Luke Johnson, Renate Kupke, Donald T. Gavel, Claire E. Max
LLNL, NSO, UCSC, UCSC, UCSC
We discuss the potential of ELTs to deliver diffraction-limited performance at visible wavelengths with laser guide stars in the light of ongoing laboratory experiments of high-order laser tomographic AO (LTAO). We simulate a high-order LTAO system for a 30-meter telescope with the LTAO/MOAO testbed at UCSC. Eight Sodium Laser Guide Stars (LGSs) are sensed by 99x99 Shack-Hartmann wavefront sensors over 75". The system is diffraction-limited (S 10%) at 800 nm over a 20” field-of-regard. Recent lenslet array upgrades reduce Shack-Hartmann nonlinearity error and thus structured systematic open-loop wavefront estimation error. We discuss attempts to include NGS tip/tilt information in the tomographic reconstruction using a split tomography method (Gilles et al. 2010).