Webb telescope mounted on top of Ariane 5 rocket in French Guiana

The James Webb Space Telescope is lifted on top of its Ariane 5 launcher inside the final assembly building in French Guiana. Credit: ESA-Manuel Pedoussaut

The nearly $10 billion James Webb Space Telescope, suspended under a crane with four cables, was raised atop top an Ariane 5 launcher Saturday inside a vertical hangar in French Guiana, one of the final steps to prep the mission for liftoff this month after a quarter-century of design and development.

A crane raised the more than 6-ton observatory on top of the rocket that will carry it into space, carefully lining its launch adapter with bolts on an attachment ring at the top of the Ariane 5, which has been assembled at the European-run Guiana Space Center over the last six weeks.

Ground teams working inside the final assembly building — known in French as the Batiment d’Assemblage Final, or BAF — carefully monitored the three-story-tall Webb telescope as a crane lifted it about 130 feet (40 meters) above the floor. The crane then translated Webb in a lateral motion to a position directly above the Ariane 5 stacked on its mobile launch platform.

“This whole process was performed under strict safety and cleanliness regulations, as it was one of the most delicate operations during the entire launch campaign for Webb,” NASA and the European Space Agency said in a joint statement.

The final assembly building is where satellites preparing for launch on Ariane 5 rockets meet their launch vehicle. But Webb, the largest space telescope ever launched, comes with special requirements to ensure its sensitive gold-plated optics, delicate sunshield, and other structures remain free of contamination.

JWST is lowered onto the attachment ring at the top of the Ariane 5 rocket, with the protective “shower curtain” around it. Credit: ESA-Manuel Pedoussaut

Teams erected a “shower curtain” nearly 40 feet tall and 26 feet (12 meters by 8 meters) around the location where Webb was lowered onto the Ariane 5 rocket. The sealed-off volume was designed to protect the observatory before its encapsulation inside the Ariane 5’s Swiss-made nose cone.

The encapsulation will pave the way for Webb’s next major move before launch. The Ariane 5 will ride its mobile launch table along rail tracks leading to the launch pad at the Guiana Space Center two days before liftoff, which is currently scheduled for no earlier than Dec. 24 at 7:20 a.m. EST (1220 GMT; 9:20 a.m. French Guiana time).

The mission was previously set for launch Dec. 22, but NASA announced Tuesday that the flight would be delayed at least two days to troubleshoot a communications issue between the observatory and its rocket. If the troubleshooting resolves the problem, the fairing could be lowered over the observatory Friday, officials said.

The James Webb Space Telescope will ride the Ariane 5 on a half-hour ascent into space, beginning a journey to the observatory’s distant operating orbit near the L2 Lagrange point, a gravitationally-neutral location about four times farther from Earth than the moon.

After a series of crucial deployments of its sunshield and mirror array, Webb will begin peering deeper into the universe than any telescope before, probing the first galaxies and stars that formed after the Big Bang more than 13 billion years ago.

Additional photos of the spacecraft’s attachment to the Ariane 5 rocket are posted below.

Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut Credit: ESA-Manuel Pedoussaut

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