Numerous investigations are presently underway at Yerkes Observatory utilizing the 41" reflecting telescope. Located in the ground floor coude room 40' below the telescope is the Wavefront Control Experiment (WCE) which was built at a cost of $85,000,000 for an experiment to be conducted on the Space Shuttle. That SDIO experiment was canceled in 1990, and the University of Chicago was awarded the WCE for fundamental astronomical investigations in 1992; it has resided here at Yerkes since mid-1994. The WCE corrects for atmospheric image distortions by measuring the wavefront and then applying signals to the actuators in a deformable mirror at a rate of 4000 times a second. It is one of the world's fastest adaptive optics systems. We are presently using it to study the harshest form of atmospheric seeing, which is when one looks at stars just over the horizon (horizontal, or "volume" turbulence); besides horrible image degradations there is also significant brightness fluctuations, or scintillation, in the source. We have set up a green laser source three miles distant on the other side of Lake Geneva to serve as a bright star source for these tests. We are testing numerous mathematical algorithms and instrumental techniques, and taking fundamental measurements, to quantify image quality seen through horizontal paths and to figure out ways to improve these images. One astronomical application is to image the planet Mercury while it is just above the horizon and still in a reasonable dark sky.
Other experiments include monitoring Jupiter for the Galileo mission team at JPL using a simple, but powerful, off-the-shelf item, called the AO-2, that corrects for image motion due to either atmospheric turbulence effects or to vibrations in the telescope system. Another are tests using a "low-order" adaptive optics unit, called the AO-5, funded by the Meyer Foundation for the Meyer-Womble Observatory on Mt. Evans in Colorado, which is on loan to Yerkes and installed in the WCE laboratory. Using that apparatus we hope to monitor the atmospheres of the planets Uranus and Neptune, and to do other interesting astronomical investigations. We have an ideal facility for testing and experimenting with novel instrumentation because we are guaranteed ample telescope time for this research, and we have an accessible and stable laboratory environment for these tests. Though the weather is not always ideal, artificial sources in the laboratory, behind the telescope, or across the lake give us varying degrees of turbulence and can be used even in cloudy weather! Considerable efforts over the previous three years have made the Yerkes 41" telescope a powerful tool for conducting leading edge adaptive optics research. We look forward to expanding our program and new collaborative arrangements with scientists throughout the world.
For further information or for answers to any questions that you may have about our work, please contact Walter Wild at (773) 702-8747, or use email at walter@troy.uchicago.edu.
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