The James Webb Space Telescope (JWST) has successfully deployed the final segment of its massive primary mirror, marking one of the most intricate space deployments in history. The mission team now focuses on aligning the mirror segments and calibrating the instruments.
Mission accomplished. On Saturday, January 8, the JWST—the largest space telescope ever built—fully deployed its primary mirror. It had to fold its "wings" during launch to fit inside the Ariane 5 rocket's payload fairing.
The observatory is set to reach its destination at Lagrange Point 2, 1.5 million kilometers from Earth, by January 23. In the coming weeks, teams will perform complex commissioning tasks, including aligning the mirror segments to function as a single optical surface.
"All segments are currently offset by a few millimeters. Our goal is to align them to within tens of nanometers—smaller than a coronavirus," explains Jane Rigby, JWST Operations Project Scientist at NASA. Engineers note that the first images will be blurry, requiring several weeks of fine-tuning for optimal performance.
Once commissioning wraps up, the team anticipates an impressive series of images to showcase the telescope's capabilities. While initial targets remain undisclosed, they may include specific stars or a nearby galaxy like the Large Magellanic Cloud to evaluate contrast and brightness resolution.
Instrument commissioning will proceed as they cool sufficiently, enabling observations across visible, near-infrared, and mid-infrared wavelengths (0.6 to 28.5 micrometers). "Each instrument has unique milestones," Rigby adds. "Calibrating them at operating temperatures while ensuring precise alignment will be challenging."
After approximately six months of commissioning, JWST will enter a five-month early science phase with early release science programs spanning six key areas, from planet formation to stellar physics.
