New Space Telescope Is Closer to Prime Time After Mirror Focusing

September 7, 2007

A set of mathematical algorithms designed to focus 19 mirrors that comprise NASA's James Webb Space Telescope has passed a major test with flying colors.

The Webb telescope is supposed to settle into its vantage point — 1 million miles from Earth — after its scheduled launch in 2013. Covering an area of 25 square meters and a diameter of 6.5 meters, the 18 primary mirrors will have to "be aligned in position so that they act as one smooth surface, and the secondary mirror be placed exactly right," said Bill Hayden, a NASA systems engineer. "This will allow scientists to clearly focus on very dim objects" in far-off regions of the universe.

Through a process called "wavefront sensing and control" (WFSC), software aboard the observatory will compute the optimum position of each of the 19 mirrors, then adjust the positions, if necessary. The underlying algorithms are designed to align and coordinate the mirrors to create one complex, extremely sensitive telescope. When the telescope takes digital pictures of, for instance, a distant star, the algorithms will process the images and then calculate mirror adjustments that result in even sharper images despite the faint light.

Engineers from Ball Aerospace & Technologies Corp. and NASA tested the WFSC algorithms on a scale model of the telescope and through computer simulations.

"This major technological accomplishment," said John Mather, senior project scientist on the Webb telescope at NASA and the 2006 winner of the Nobel Prize in Physics, was "built on the legacy of software algorithms used to fix the Hubble Space Telescope and align the Keck telescope."

Source: NASA, Aug. 24, 2007.