Artist’s concept of the James Webb Space Telescope with one half of its sunshield deployed. Credit: NASA

Flying outbound from Earth at a distance of more than 400,000 miles, the James Webb Space Telescope extended one of two booms Friday to begin unfurling the mission’s five-layer sunshield. With the port-side boom deployed, work is underway tonight to extend another boom on the starboard side.

The critical deployments mark some of the most nail-biting moments to ready the nearly $10 billion observatory for science operations, following its successful launch Dec. 25 aboard a European Ariane 5 rocket.

NASA confirmed the successful extension of the port-side mid-boom in an update shortly after 7 p.m. EST Friday (0000 GMT Saturday).

Ground teams started extending the two sunshield booms several hours later than originally scheduled, NASA said in an update Friday evening. The space agency said mission controllers at the Space Telescope Science Institute took extra steps to confirm that a sunshield cover had fully rolled up before proceeding with the first mid-boom deployment.

“Switches that should have indicated that the cover rolled up did not trigger when they were supposed to,” NASA said. “However, secondary and tertiary sources offered confirmation that it had. Temperature data seemed to show that the sunshield cover unrolled to block sunlight from a sensor, and gyroscope sensors indicated motion consistent with the sunshield cover release devices being activated.”

The covers were opened and rolled back to expose the sunshield to space Thursday.

Five telescoping segments fo the port, or left-side, mid-boom began extending around 1:30 p.m. EST (1830 GMT) Friday. The motor-driven boom reached full deployment at 4:49 p.m. EST (2149 GMT), NASA said.

Officials have repeatedly said Webb’s deployment schedule could change based on real-time conditions. Friday’s activities showed the ground team’s flexibility.

Managers decided Friday evening to move forward with extending the starboard mid-boom, and initial steps for that deployment began shortly after 7 p.m. EST (0000 GMT), NASA said.

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– Spaceflight Now