Which JWST mirror wing was latched into place to complete the telescope's major deployment on January 8, 2022?

The starboard primary mirror wing was latched into place on 8 January 2022.

Webb's primary mirror is made from 18 hexagonal segments, but the full mirror could not fit inside the Ariane 5 rocket's nose cone. Engineers therefore folded six segments into two side wings for launch. After deployment in space, each wing had to swing outward and lock into its operating position.

The port-side wing was deployed and secured first, on 7 January. The starboard-side wing followed on 8 January, completing the observatory's major structural deployment. Each wing carried three primary-mirror segments, so this final step restored the telescope's full 6.5-metre primary mirror configuration.

This event is distinct from the deployment of the secondary mirror, which occurred earlier, on 5 January. It is also not the same as deploying the sunshield, whose five membranes were tensioned before the mirror wings. Once the wings were latched, Webb still required months of mirror alignment, instrument checks, and commissioning before beginning science observations.