The final part of the James Webb Space Telescope’s 21-foot mirror swung into place Saturday at flight controllers’ command, completing what NASA has billed as one of its most complicated deployments in space ever.
The main part of the telescope’s gold-plated, flower-shaped mirror is made of beryllium, a lightweight yet sturdy and cold-resistant metal. Each of its 18 segments is coated with an ultra-thin layer of gold, highly reflective of infrared light.
The hexagonal, coffee table-size segments must be adjusted in the weeks ahead so they can focus as one on stars, galaxies, and alien worlds that might hold atmospheric signs of life.
“It’s like we have 18 mirrors that are right now little prima donnas all doing their own thing, singing their own tune in whatever key they’re in, and we have to make them work like a chorus and that is a methodical, laborious process,” operations project scientist Jane Rigby told reporters.
On January 23, 2022, Webb is expected to arrive at its “insertion location.” This will put the telescope in place to fire its engines allowing it to glide to its “parking spot,” called Earth-sun Lagrange Point 2 (L2) about 930,000 miles (1.5 million kilometers) away from our planet.
Lagrange Points are positions in space where the gravitational forces of a two-body system like the Sun and the Earth produce enhanced regions of attraction and repulsion.
By getting to this L2 position, Webb can use a minimum of fuel to stay in place thanks to a near-perfect alignment with the sun, Earth, and moon.
There is more maneuvering the control teams will need to execute in the weeks to come. Webb still has a lot of complex commissioning operations ahead, and NASA particularly pointed to aligning its mirror and getting its instruments ready as key milestones to watch for in the next few weeks.
As control teams look to the upcoming firing of Webb’s engines, they will spend the next 15 days aligning the telescope’s 18 segmented mirrors to “essentially perform as one mirror,” John Durning, Webb’s deputy project manager at NASA’s Goddard Space Flight Center told reporters.
“I should say also, that Webb will start turning on the instruments in the next week or so,” Durning added. “And then after we get into L2, as the instruments get cold enough, they [engineers] are going to be starting to turn on all the various instruments.”
