Mirror, Mirror...

About the only times I think about mirrors are when: (1) I have to readjust the rear-view mirrors on my motorscooter, or (2) when I'm in the barbershop looking at the mirror in front of me that reflects the mirror behind me which reflects the mirror in front of me....

I admit I have a hard time controlling one mirror on my scooter, let along both of them. They just keep moving around. Which leads me to admire what the engineers working on the James Webb Space Telescope have done. They've been able to control the 19 individual mirrors comprising the telescope, enabling the mirrors to function as one. And they'll be doing it from a million miles away.

The James Webb Space Telescope is a large, infrared-optimized space telescope, scheduled for launch in 2013. Its 18 primary mirror segments cover a combined total area of 25 square meters (approximately 30 square yards) and a diameter of 6.5 meters (about 21 feet). and a sunshield the size of a tennis court. Since the mirror and sunshade won't fit onto the rocket fully open, they will fold up and open only once the telescope is in outer space. It will eventually reside in an orbit about 1.5 million km (1 million miles) from the Earth.

The orientations of the telescope’s 18 primary mirror segments and the position of the secondary mirror will be adjusted to bring light from the universe into focus through a process called Wavefront Sensing and Control (WFSC). The software aboard the observatory will compute the optimum position of each of the 19 mirrors, then adjust the positions, if necessary

The WFSC system is put to work when the telescope takes digital pictures of a star. It then processes the images through mathematical algorithms to calculate the mirror adjustments required to bring the stellar image into focus. When the individual mirrors are properly aligned, the Webb Telescope will be able to obtain extraordinarily sharp images and detect the faint glimmer of a distant galaxy.

Recently, a team of engineers from Ball Aerospace & Technologies and NASA successfully tested the WFSC algorithms, proving they are ready to work on the Webb Telescope in space. The algorithms were tested on a detailed scale model of the 6.5 meter space telescope and through computer simulations.

"This major technological accomplishment, which built on the legacy of software algorithms used to fix the Hubble Space Telescope and align the Keck telescope, is a major step forward in the development of JWST. This achievement was the result of great teamwork between Ball Aerospace, NASA Goddard Space Flight Center, and the Jet Propulsion Laboratory," said John Mather, Senior Project Scientist on the Webb telescope at Goddard and the 2006 winner of the Nobel Prize in Physics.

Posted by Jon Erickson at 11:41 AM  Permalink