Optical technologies for extremely-large telescopes

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Future advances in our knowledge of the Universe will require new powerful telescopes on Earth and in space, with a resolution and sensitivity 10 to 100 times greater than present facilities. These telescopes, now being designed by astronomers and engineers worldwide, will achieve their power by a combination of large aperture and advanced technologies. One of these technologies, adaptive optics, is key to all future large ground-based telescopes because it can largely correct for the blurring effect of turbulence in the atmosphere. Next-generation AO systems will require high-powered lasers and sophisticated computer-controlled deformable mirrors. The lasers are used to illuminate sodium atoms, deposited by meteors in the upper atmosphere, in order to produce artificial "reference stars". The light from these sodium "stars" is needed to measure, and then correct for, the turbulence. To design these systems, we must first understand the structure of Earth's sodium layer. By combining a 6-metre liquid-mirror telescope with a sophisticated laser and detector system, my team has developed a sodium lidar (laser radar) that produces data of unsurpassed quality. My students and I will use this facility to study and better understand the structure and dynamics of this important region of the atmosphere, and provide knowledge essential for the development of extremely large telescopes.