With the aid of a robotic arm, scientists and engineers installed the final mirror making up the primary mirror segment for the James Webb Space Telescope.

NASA’s John Grunsfeld gave the team a well-deserved congratulations.

Originally posted February 5, 2016.

“Scientists and engineers have been working tirelessly to install these incredible, nearly perfect mirrors that will focus light from previously hidden realms of planetary atmospheres, star forming regions and the very beginnings of the Universe.” Grunsfeld added, “With the mirrors finally complete, we are one step closer to the audacious observations that will unravel the mysteries of the Universe.”

We’ve been hearing about the James Webb Space Telescope for years. It’s great to finally see it come together.

Lee Feinberg, an optical telescope element manager at Goddard, called it a “very significant milestone and the culmination of over a decade of design, manufacturing, testing and now assembly of the primary mirror system.”

The mirrors

They were built by Ball Aerospace & Technologies Corp., and they are massive. Each of the 18 hexagon-shaped mirrors is just over 4.2 feet across and weigh 88 pounds. Now, I see why they needed a robotic arm.

JWST mirror

Once in space and deployed, each 4.2-foot mirror will work together as one giant 21.3-foot diameter mirror.

How does that stack up against some of the largest telescopes in space right now? The Hubble Space Telescope’s mirror comes in at just 7.9 feet. While the largest infrared space telescope, Herschel, packs an 11.5-foot mirror.

Here’s a video showing the installation of the first mirror back in December. You can see just how painstakingly careful engineers have to be when installing each mirror.

What’s next for the James Webb Space Telescope

The installation of all 18 mirrors is an important milestone, but there’s still a lot of work to be done. Next up? Installation of other optics and a battery of tests to make sure the telescope can handle a bumpy rocket launch.

Gary Matthews, director of Universe Exploration at Harris Corporation, explains their part in assembling the telescope.

“The Harris team will be installing the aft optics assembly and the secondary mirror in order to finish the actual telescope,” said Matthews. “The heart of the telescope, the Integrated Science Instrument Module, will then be integrated into the telescope. After acoustic, vibration, and other tests at Goddard, we will ship the system down to Johnson Space Center in Houston for an intensive cryogenic optical test to ensure everything is working properly.”

The Integrated Science Instrument Module contains the telescopes four science instruments:

Near-Infrared Camera (NIRCam)
Near-Infrared Spectrograph (NIRSpec)
Mid-Infrared Instrument (MIRI)
Fine Guidance Sensor/Near-Infrared Imager and Slitless Spectrograph (FGS/NIRISS)

Here’s a short video showing where the instruments are situated onboard the James Webb Space Telescope.

As you can see, the James Webb Space Telescope is an infrared telescope.

The NIRCam is the primary imager for the telescope. It will observe the cosmos in an infrared wavelength range from 0.6 to 5 microns. Its main targets will be the earliest stars, galaxies, planets and even Kuiper Belt Objects. It’s what the telescope may be able to tell us about exoplanets that have many excited. Using coronagraphs, astronomers can block the light from an exoplanet’s host star, and hopefully, figure out the characteristics of the planets.

The NIRSpec looks at the same wavelengths of the NIRCam but pays close attention to an object’s spectrum. Careful analysis of this spectrum gives scientists a good idea about the physical properties of an object. Things like mass, chemical composition and temperature.

Did You Know: NIRSpec will be able to observe 100 objects simultaneously thanks to a new microshutter system.

The MIDI contains a camera and a spectrograph. While the other instruments focus on near-infrared, MIDI focuses on the wavelength range of 5 to 28 microns. You know all those incredible pictures the Hubble is known for? MIDI will keep that tradition alive on the James Webb Space Telescope.

The FGS/NIRISS is the most important instrument of them all. It helps point the telescope. The NIRISS part will be on the lookout for exoplanets.


The next generation of space telescope is almost here. If everything else goes smoothly, the James Webb Space Telescope will begin a new age of discovery when it launches from French Guiana in 2018.

When I’m not playing Rocket League (best game ever), you can find me writing about all things games, space and more. You can reach me at alex@newsledge.com

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