NASA completes mirror polishing for James Webb Space Telescope

June 30, 2011
This image shows the four different types of mirrors on the Webb telescope. From left to right are: a primary mirror segment, the secondary mirror, tertiary mirror and the fine steering mirror. The bottom right shows an artist's conception of the Webb telescope optics with its 18 primary mirror segments. Credit: NASA/Ball Aerospace/Tinsley

Mirrors are a critical part of a telescope. The quality is crucial, so completion of mirror polishing represents a major milestone. All of the mirrors that will fly aboard NASA's James Webb Space Telescope have been polished so the observatory can see objects as far away as the first galaxies in the universe.

The Webb telescope is comprised of four types of mirrors. The primary one has an area of approximately 25 square meters (29.9 square yards), which will enable scientists to capture light from faint, distant objects in the universe faster than any previous . The mirrors are made of and will work together to relay images of the sky to the telescope's science cameras.

"Webb's mirror polishing always was considered the most challenging and important technological milestone in the manufacture of the telescope, so this is a hugely significant accomplishment," said Lee Feinberg, Webb manager at NASA's Goddard Space Flight Center in Greenbelt, Md.

The mirrors were polished at the L3 Integrated - Tinsley in Richmond, Calif. to accuracies of less than one millionth of an inch. That accuracy is important for forming the sharpest images when the mirrors cool to -400°F (-240°C) in the cold of space.

This video is not supported by your browser at this time.
The episode of "Behind the Webb" called "Wax On, Wax Off" focuses on some of the processes that go into making the mirrors on the Webb telescope so powerful. Credit: STScI/Mary Estacion

"The completion of the mirror polishing shows that the strategy of doing the hardest things first has really paid off," said Nobel Prize Winner John C. Mather, Webb's senior project scientist at Goddard. "Some astronomers doubted we could make these mirrors."

After polishing, the are being coated with a microscopically thin layer of gold to enable them to efficiently reflect infrared light. NASA has completed coating 13 of 18 primary mirror segments and will complete the rest by early next year. The 18 segments fit together to make one large mirror 21.3 feet (6.5 meters) across.

"This milestone is the culmination of a decade-long process," said Scott Willoughby, vice president and Webb Telescope Program manager for Northrop Grumman Aerospace Systems. "We had to invent an entire new mirror technology to give Webb the ability to see back in time."

NASA engineer Ernie Wright looks on as the first six flight ready James Webb Space Telescope's primary mirror segments are prepped to begin final cryogenic testing at NASA's Marshall Space Flight Center in Huntsville, Ala. Credit: NASA/MSFC/David Higginbotham

Northrop Grumman Corp. in Redondo Beach, Calif. is the telescope's prime contractor.

As the successor to the Hubble Space Telescope, the Webb telescope is the world's next-generation space observatory. It is the most powerful ever built. More than 75 percent of its hardware is either in production or undergoing testing. The telescope will observe the most distant objects in the universe, provide images of the first galaxies ever formed and study planets around distant stars. NASA, the European Space Agency and the Canadian Space Agency are collaborating on this project.

Explore further: James Webb Space Telescope Completes Cryogenic Mirror Test

Related Stories

Two kinds of Webb telescope mirrors arrive at NASA Goddard

April 13, 2011

It takes two unique types of mirrors working together to see farther back in time and space than ever before, and engineers at NASA's Goddard Space Flight Center have just received one of each type. Primary and Secondary ...

NASA's next generation space telescope marks key milestone

April 15, 2011

( -- The first six of 18 segments that will form NASA's James Webb Space Telescope's primary mirror for space observations will begin final round-the-clock cryogenic testing this week. These tests will confirm ...

Recommended for you

NASA selects investigations for future key planetary mission

October 1, 2015

NASA has selected five science investigations for refinement during the next year as a first step in choosing one or two missions for flight opportunities as early as 2020. Three of those chosen have ties to NASA's Jet Propulsion ...

Dawn team shares new maps and insights about Ceres

October 1, 2015

Mysteries and insights about Ceres are being discussed this week at the European Planetary Science Conference in Nantes, France. NASA's Dawn spacecraft is providing scientists with tantalizing views and other data about the ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.