Characterization and mitigation of Laser–Guide–Star–induced aberrations

¹ AO Laboratory, Mechanical Engineering Department, University of Victoria, BC, Canada
² NRC–Herzberg Institute of Astrophysics, Victoria, BC, Canada

^a e-mail: lardiere@uvic.ca

Abstract

Sodium Laser Guide Stars (LGS) induce optical aberrations in adaptive optics (AO) systems. The artificial star is elongated due to the sodium layer thickness, and the variations of the sodium layer altitude and atom density profile induce errors on centroid measurements of elongated spots. In AO systems, these errors generate spurious optical aberrations, termed LGS aberrations, especially with ELTs for which the spot elongation is greater. According to analytical models and experimental results obtained with the University of Victoria LGS bench demonstrator, we characterized the main LGS aberrations and studied two options to mitigate them: the Radial Thresholding and the temporal filtering.