Ariane 5 launch of JWST
ESA and Arianespace said they are finalizing corrective actions to address a payload fairing separation issue sene on two Ariane 5 launches in 2020, setting up for a launch of JWST no earlier than November. Credit: ESA - D. Ducros

WASHINGTON — NASA’s James Webb Space Telescope is finally scheduled to launch Dec. 18 on an Ariane 5 from French Guiana after years of development delays.

NASA, the European Space Agency and Arianespace announced Sept. 8 that they had selected Dec. 18 as the formal targeted launch date for the giant space observatory. ESA is providing the launch as part of its contribution to the NASA-led mission in exchange for a share of observing time.

The mid-December date is slightly later than previously anticipated. NASA had been advertising a launch readiness date of Oct. 31, but noted that the launch would take place after two Ariane 5 launches, spaced roughly two months apart. One, carrying two communications satellites, took place July 30.

Arianespace said the second, carrying the SES-17 and Syracuse-4A satellites, is now scheduled for Oct. 22, rather than late September as previously expected.

The July 30 launch was the first for the Ariane 5 in nearly a year in order to correct issues with the separation of the vehicle’s payload fairing seen in two launches in February and August 2020. On those launches the release of the fairing imparted loads on the payload stack higher than expected, but did not damage the satellites.

During a Sept. 6 webinar by the Asia-Pacific Satellite Communications Council, Vivian Quenet, managing director and head of sales in the Asia-Pacific region for Arianespace, said the July launch did not experience the same payload fairing issues seen on the two 2020 Ariane 5 launches.

“There was a clamp issue, and some noise and vibration that shouldn’t be there,” he said of the earlier launches. “The problem is solved.”

JWST itself is being prepared for shipment from a Northrop Grumman facility in Southern California to French Guiana. NASA announced Aug. 26 it had completed the final testing of the spacecraft and was in the process of packaging it for shipment. The telescope will be transported by ship, via the Panama Canal, to French Guiana, arriving in October to begin final launch preparations.

“We are on track, the spaceport is busy preparing for the arrival of this extraordinary payload, and the Ariane 5 elements for this launch are coming together,” Daniel Neuenschwander, ESA’s director of space transportation, said in a statement. “We are fully committed, with all Webb partners, to the success of this once-in-a-generation mission.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...