Feb. 20, 1998 HOUGHTON, MI--Mike Roggemann and Tim Schulz, researchers in Michigan Technological University's Electrical Engineering Department, are developing new techniques to sense distortions in space telescopes.
The goal of the project is to sense wave front errors on the thin mirrors of large space telescopes. "To lighten mirrors as much as possible for launch," says Roggemann, associate professor of electrical engineering, "mirrors are being made thinner and therefore less mechanically stable with every new telescope.
"In the space environment, the mirrors are very susceptible to vibrations from pointing the telescopes at differnt targets and also to thermal stresses caused by the telescopes passing in and out of Earth's shadow." In space, as Earth follows a path around the sun, shadows trail behind. Since no heat from the Sun can warm the shadow, temperatures fall to extreme levels.
Subjected to such stresses, "the clarity of the telescope mirrors becomes comparible to the eyesight of a person wearing glasses," says Roggemann. "The big, thin mirrors can have large aberations in their shape so that focusing becomes difficult. When a person needs glasses, an eye doctor tests a range of possible corrective lenses. In space, the aberation change time, and can't constantly be monitored by humans.
"A common aberation in space telescopes measures a few microns," says Roggemann. "That is a huge error in optical terms." The aberations, once sensed, can be corrected by mechanisms pushing and pulling the mirrors from inside.
Roggemann and Schulz developed algorithms to measure the wave fronts with software and are working on a lab experiment to demonstrate the technology. With this application, space exploration can continue to expand into new territory by providing ways for space telescopes like the Hubbel to focus properly.
The project is being supported by a grant of $184,000 from Select Tech Services through the Air Force Ofice of Scientific Research.
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