The James Webb Space Telescope (JWST) has unfolded exactly as planned just over two weeks into the mission. On Saturday, NASA controllers announced that the telescope’s final primary mirror section had locked into place, bringing the space telescope’s deployment phase to completion.
“Today, NASA achieved another engineering milestone decades in the making,” says Bill Nelson (NASA Administrator) in a press release. “While the journey is not complete, I join the Webb team in breathing a little easier and imagining the future breakthroughs bound to inspire the world.”
On December 25, 2021, JWST was launched from the Guiana Space Center on an Ariane 5 rocket. The telescope’s separation from the second stage, the unfolding and tensioning of its sunshield, among other steps toward full deployment, have all occurred in the last few weeks.
The observatory features a 6.5-meter (21.6-foot) primary mirror and a sunshield the size of a tennis court, both of which had to fold up to fit inside the Ariane 5 rocket fairing before carefully unfolding in space after launch.
The Contamination Control Cover for ESA’s Mid-Infrared Instrument (MIRI) was unlocked on January 5th. This cover shielded MIRI from ice contamination during and after launch in place of standard heater units. On January 5th, the telescope’s secondary mirror was also deployed, and on January 6th, the heat radiator (Aft Deployable Instrument Radiator, ADIR) was also successfully deployed.
The deployment of JWST’s 18-segment primary mirror took place on January 7th and 8th, bringing the deployment phase to an end. The primary mirror consists of three panels: a centre section and two “wings” folded out and locked into place.
You might be wondering why there aren’t any cameras on JWST. While viewing the actual unfolding process would have been intriguing, the mission team didn’t include cameras because they would have added extra cost to an already over-budget, $11 billion project. Moreover, the cameras would have had to be sealed and built specifically to operate in ultra-cold and dark conditions while not producing heat in a system that must be kept extremely cold.
JWST will use six actuators attached to the back of each section to shift its 18 unique mirror segments out of their launch configuration during the next few days. The telescope will next enter a halo orbit at the Sun-Earth L2 point, 1.5 kilometres (1 million miles) from Earth, around January 23rd, 29 days after launch. Scientific operations will start in mid-2022; once the telescope cools to below 50K (-370°F), mirror orientation is tweaked to bring images into focus, and sensors are calibrated.
By viewing galaxies and stars developing in the early universe, characterising the chemical composition of exoplanet atmospheres, and much more, JWST is expected to push the boundaries of modern astronomy.
JWST has fully unfurled, is healthy, and is getting to its new home near L2.