James Webb Space Telescope Successfully Deploys Its Mirror for the First Time
NASA has scaled back work on the James Webb Space Telescope in light of the ongoing coronavirus pandemic, but the Northrop Grumman team took a big step toward getting it into space last month. In an early March test, engineers deployed the telescope’s multi-segment mirror in its final configuration for the first time. It’s quite a sight to behold, but we might have to wait longer than expected to see it in action.
The Webb telescope is currently in a cleanroom at Northrop Grumman Space Systems in Redondo Beach, California. The telescope is fully assembled and connected to a system of gravity-compensating supports that simulate the conditions it will experience in space. That allows the team to conduct tests on the telescope and confirm it will work as intended.
When it begins operating, the James Webb Space Telescope (JWST) will have the largest primary mirror of any space-based imaging system. The telescope’s primary mirror is 6.5 meters (21 feet) across, composed of 18 hexagonal segments of gold-plated beryllium. Hubble’s mirror is comparatively tiny at 2.4 meters (almost 8 feet). In order to get such a large mirror into space, the JWST needs to fold up to fit inside the Ariane 5 launch vehicle. Deploying the mirror after launch is perhaps the most critical part of the mission. If the mirror doesn’t come together just right, the instrument won’t work correctly, and it may not be possible to send a repair mission.
In the March test, engineers signaled the JWST to deploy its mirror for the first time. The Ariane 5 payload fairing is five meters across. So, the middle section of the mirror was built as a single unit. There are left and right “wings,” each with three panels that need to swing into place. The telescope’s internal electronic systems unfolded the mirror segments perfectly in this test. The Webb team will only deploy the mirror one more time before packing the telescope up for delivery to the launch site.
We don’t know when the JWST will make it to space, though. The telescope is still technically on the schedule for a March 2021 launch, but NASA announced last week that it had suspended work on the project because of coronavirus concerns. If the situation doesn’t improve soon, NASA may have to push back the launch yet again. There’s still a lot of testing to do before the telescope can safely begin its mission.