Laser tomography adaptive optics subsystem for GMT

The Giant Magellan Telescope (GMT) is being designed and built by an international consortium of institutions and will be the largest optical telescope in the world when it is completed around 2020. The GMT will rely on cutting edge adaptive optics (AO) technologies to correct for the blurring caused by the Earth's atmosphere and achieve images sharper than those that can be obtained by space-based telescopes. 

The telescope will be located on the summit of Las Campanas in Chile, a site unparalleled for optical observing with its very clear, dark skies and dry, thin air. Even at such a location, turbulence in the Earth's atmosphere causes distortions to the light travelling through it  that limit the sharpness of the images that are recorded. Modern telescopes use a technique known as adaptive optics (AO) to compensate for these distortions with mirrors that can are deformed to account for the errors.

A team of AO and instrumentation engineers and scientists at RSAA are designing one of the AO systems for the GMT: the laser tomography adaptive optics (LTAO) subsystem. This will use six high-power lasers to generate artificial 'guide' stars in the sky. These are observed and their images measured to determine the distortions across a relatively wide area of the sky. A high-speed control loop will continuously make these measurements and use them to deform the correcting mirrors in such as way as to reduce the effects of the atmospheric blurring.

The LTAO system will be used to correct the light collected by the telescope before it is fed to back-end instruments that analyse and record it. The GMT Integral-Field Spectrograph (GMTIFS) will be the first instrument to use this cutting-edge AO system and is also being designed and built for the GMT by the technical team at RSAA.

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