Spaceflight Insider

Completion of primary mirror marks milestone for James Webb space telescope

Inside a massive clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland, the James Webb Space Telescope team used a robotic arm to install the last of the telescope's 18 mirrors onto the telescope structure.

Inside a massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the James Webb Space Telescope team used a robotic arm to install the last of the telescope’s 18 mirrors onto the telescope structure. (Click for expanded view.) Photo & Caption Credit: NASA / Chris Gunn

The James Webb Space Telescope, dubbed the successor to the Hubble Space Telescope, and the most powerful space-based observatory ever constructed, reached a major milestone recently when its 18th and final primary mirror was installed on February 3.

Engineers and scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have worked on the construction and installation of the hexagon-shaped mirrors, each of which has a diameter of 4.2 feet (1.3 meters) and a weight of approximately 88 pounds (40 kg). The work was done in a large clean-room located at Goddard.

The James Webb Space Telescope fitted with all 18 mirrors.

In this rare view, the James Webb Space Telescope’s 18 mirrors are seen fully installed on the James Webb Space Telescope structure at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Photo & Caption Credit: NASA / Chris Gunn

Northrop Grumman was selected by NASA in 2002 as the primary contractor for design, construction, and integration of the James Webb Space Telescope.

The 18 hexagonal mirror segments, installed via a robotic arm, will function together as a single 21.3-foot (6.5-meter) mirror once the telescope is positioned in space.

Lee Feinberg, Goddard optical telescope element manager, said that the completion of the primary mirror is the result of more than a decade of manufacturing, testing, and assembling by a large team from around the country.

Scheduled for launch from the spaceport at Kourou,French Guiana in 2018 via an Ariane 5 rocket, the James Webb Space Telescope will study a range of astronomical and cosmological issues, including the many phases that make up the universe’s history, the evolution of the Solar System, and the formation of other solar systems with Earth-like planets in their habitable zones potentially capable of supporting life.

“Scientists and engineers have been working tirelessly to install these incredible, near perfect mirrors that will focus light from previously hidden realms of planetary atmospheres, star-forming regions, and the very beginnings of the universe,” noted John Grunsfeld, associate administrator for NASA’s Science Mission Directorate.

“With the mirrors complete, we are one step closer to the audacious observations that will unravel the mysteries of the universe,” he emphasized.

The tennis-court-sized infrared telescope is far from complete. The next steps include installing the other optics and testing each of the telescope’s components to assure all are capable of enduring a rocket launch, explained project manager Bill Ochs.

Ball Aerospace and Technologies Corporation, which designed and built the mirrors, is Northrop Grumman’s primary subcontractor for the telescope’s optics system.

Construction and launch of the telescope is a collaborative effort among NASA, the European Space Agency (ESA), and the Canadian Space Agency.

At the heart of the James Webb Space Telescope will be its Integrated Science Instrument Module, said Harris Corporation’s director of Universe Exploration Gary Matthews.

Harris Corporation employees will now install the remaining optics, including the secondary mirror, Matthews said.

Once all the telescope’s parts are integrated, a series of tests, including studies of its acoustic and vibration systems, will be conducted at Goddard.

After these tests are completed, the telescope will be sent to NASA’s Johnson Space Center in Houston, Texas, where it will be subject to an “intensive cryogenic optical test to ensure everything is working properly,” Matthews said.

Interested viewers can watch the construction of the telescope proceed at Goddard’s “Webb-cam” page by clicking here.


Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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