December 25, 2021

— The world's largest and most powerful space telescope has made it safely off the planet, but it still has a complex deployment and a million-mile journey before it can start revealing the universe like never before.

The James Webb Space Telescope (JWST), named after the Apollo-era NASA administrator who championed space science, is an infrared observatory that will be used to image the earliest galaxies and to discern the atmospheric properties of exoplanets. It is intended as the scientific successor for the Hubble and Spitzer space telescopes, which remain in operation.

"The James Webb Space Telescope is an Apollo moment for all of NASA, for the entire world, but especially for our science programs worldwide. It's the stuff of dreams," said Thomas Zurbuchen, NASA's associate administrator for science, in a pre-launch press briefing. "We've never built a space telescope this big and this complex. Frankly, it's the largest international space project in science and in U.S. history."

On Saturday (Dec. 25), an Ariane 5 rocket carrying the intricately-folded Webb lifted off from Arianespace's ELA-3 launch complex at Europe's Spaceport located near Kourou, French Guiana. The 7:20 a.m. EST (1220 GMT or 9:20 a.m. local time) launch began a 27-minute powered climb into space that culminated in the telescope separating from its rocket's upper stage and automatically deploying its solar array within a half hour of leaving Earth.

"It is a great day for planet Earth," said NASA Administrator Bill Nelson, reflecting on the launch soon after Webb extended its solar array. "This telescope is now going to take us back in time. It's a time machine. It's going to take us back to the very beginnings of the universe."

"We are going to discover incredible things that we never imagined," said Nelson.

James Webb Space Telescope launch. Click to enlarge video in a pop-up window. (NASA)

Unlike past space telescopes, Webb's liftoff marked only the beginning of its deployment. The observatory was launched on a direct path to an orbit around the second Lagrange Point (L2), a position in space about a million miles (1.5 million kilometers) directly behind Earth (as viewed from the Sun) where the gravity of the Sun and Earth balances the centripetal force required for the spacecraft to move with them.

Three midcourse corrections, the first scheduled for 12 hours after the launch, will be required to insert Webb into the optimum orbit around L2.

On its way there, the Webb will be commanded to slowly unpack itself, from a configuration small enough to fit into the Ariane rocket's payload fairing (about 15 feet [4.57 meters] in diameter and 53 feet [16.19 meters] in height) to a final deployed layout with a 21-foot-wide (6.5 meters) primary mirror and a sunsheid roughly the size of a tennis court.

"We've always known that this project would be a risky endeavor but, of course, when you want a big reward, you have to usually take a big risk," said Nelson at a pre-launch briefing. "It's one of the great engineering feats, not just of NASA and its international partners, but also for all of the people of this planet."

344 single points of failure

"Landing on Mars has roughly a third of the single point failures than deploying the telescope fully, so it really is a level of complexity that's over and above," said Zurbuchen.

In total, the James Webb Space Telescope has 344 single points of failure — of which about 80 percent are associated with its deployment. The telescope has 144 release mechanisms, all of which must work perfectly for Webb to operate.

"We do have multiple contingency plans," said Mike Menzel, the mission's lead systems engineer at Goddard Space Flight Center in Maryland. "There's only one deployment really that is time critical and that's to get the solar array out."

After that and the automatic deploy of the telescope's high gain antenna about two hours after launch, each step will be commanded from the ground when the team is ready to proceed.

Should all proceed to plan, the deployments will pick up again after the second trajectory correction burn about two and a half days after launch. The fore and aft sunshield pallets will be extended, followed by the release of sub-system launch locks. The telescope will then move apart from its spacecraft bus by about 6.5 feet (2 meters).

At six days, the plan is to deploy the telescope's secondary mirror, followed by the side wings of the primary mirror. By the end of the first week of flight, deployment of the full sunshield will be initiated, including the tensioning of its membranes.

The sunshield is designed to always face the Sun, Earth and moon, blocking their heat and light from reaching the telescope's heat-sensitive optics. Temperatures on the sun side of the shield will reach a maximum of about 383K (230 degrees F or 110 degrees C) and on the mirror/instruments side, a minimum of approximately 36K (-394 degrees F or -236 degrees C).

As the telescope cools down in the shade of the deployed sunshield, attention will turn to powering on the electronics and flight software. Assuming everything is in working order, then the final course correction burn will come at the end of the first month, placing Webb into its final orbit around L2.

At 33 days, Webb will be ready to take its first picture: an out-of-focus shot of a crowded star field in order to test that light is getting through the telescope into its instruments. At 44 days after launch, adjustments to the primary and secondary mirror segments will begin to sharpen Webb's view.

By the end of the third month, again assuming all proceeds to plan, the Webb will be able to take the first science-quality images. It won't be for another 25 days, though, until the view is optimized. Science operations are expected to begin soon after the six-month mark from launch.

A decade of discoveries

First proposed in 1996, the James Webb Space Telescope is a collaboration between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

NASA is responsible for the overall Webb mission, while ESA has provided the telescope's Near-Infrared Spectrograph (NIRSpec) and about half of the Mid-Infrared Instrument (MIRI), as well as provision of the Ariane 5 launch vehicle. CSA contributed the Fine Guidance Sensor (FGS) and Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument.

As an infrared observatory, Webb will be able to see through the dense molecular clouds that hide star and planet formation. It will also be able to see further back in time, to just after the creation of the universe, due to cosmological redshifting.

Using it spectrographs, Webb will also be able analyze the physical and chemical properties of planetary systems, including the planets in our own solar system, and investigate the potential for life in those systems.

"Webb will transform our view of the universe," said Nelson. "It's a revolutionary technology that will study every phase of 13 and a half billion years of cosmic history."

Given its position at L2, Webb was not designed to be serviced by astronauts. The telescope's lifespan is limited by the proper functioning of the spacecraft and instruments and by the fuel it uses for maintaining its orbit. Webb launched with enough fuel for a nominal 10-year mission.