EAGER: Composite Adaptive Mirrors

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Telescopes on the ground must observe objects in deep space through the interference of the earth's atmosphere. As light passes through the atmosphere it gets spread out by turbulence due to wind shear and changes in temperature and pressure within the atmospheric layers which effectively diminishes the resolving power of earth-based telescopes. This difficulty can be overcome to a large extent by relatively new techniques employing "Laser Guide Stars" and "Adaptive Optics." A bright laser illuminates a patch of sky near the target object. The laser's light is absorbed and then re-emitted by atoms in the upper atmosphere, above much of the interfering lower atmosphere. The return signal can then be used to track the time-dependent scattering of the light. Adaptive Optics uses this information to adjust optics in the telescope's instrumentation to restore the image to what would be seen from above the atmosphere.In order to make this work astronomers have had to divert the light path from the telescope to an optical bench where a "deformable mirror" modifies the optical beam to correct for the distortions. The corrected beam then must be piped back into the science instruments. Recently, however, some observatories have been developing adaptive secondary mirrors, making the adjustments within the telescope beam itself. (The secondary mirror is typically the second mirror in a telescope's optical chain and it reflects light from the primary mirror back down into the science instruments.) The problem with this is that secondary mirrors tend to be relatively large - much larger than current deformable mirrors; consequently making large adaptive mirrors using current technology is very costly. Dr. Christ Ftaclas of the University of Hawaii is investigating a new scheme to make adaptive mirrors that, if successful, would be less expensive and enable even larger adaptive mirrors. The ultimate goal of adaptive optics would be to make the telescope's primary mirror adaptive and with Dr. Ftaclas' idea this may become a reality. His work is funded by NSF's Division of Astronomical Sciences under an Early-concepts Grant for Exploratory Research (EAGER).