Nasa’s James Webb Space Telescope completes full assembly

The $10bn telescope was finished years late at a cost far higher than planned, but was finally launched on Christmas Day and is already more than halfway towards its destination approximately one million miles from Earth.

This initial deployment phase sparked anxiety in the teams of engineers that designed it as it had 344 single points of failure when it left the Earth and no way to correct any physical problems should anything go wrong. The most complicated and critical task, unrolling and stretching out its tennis-court-sized sunshield, was completed last week.

This included pins that had to release, latches to lock into place and a host of other mechanisms that needed to perform as planned.

With the full deployment of its 6.4 metre, gold-coated primary mirror over the weekend, Nasa has confirmed that the satellite is now ready to begin preparing for its main mission.

The satellite is a joint effort with Nasa, the European Space Agency (ESA) and the Canadian Space Agency. It is designed to explore every phase of cosmic history – from within our solar system to the most distant observable galaxies in the early universe.

“Today, Nasa achieved another engineering milestone decades in the making. While the journey is not complete, I join the Webb team in breathing a little easier and imagining the future breakthroughs bound to inspire the world,” said Nasa administrator Bill Nelson.

“The James Webb Space Telescope is an unprecedented mission that is on the precipice of seeing the light from the first galaxies and discovering the mysteries of our universe. Each feat already achieved and future accomplishment is a testament to the thousands of innovators who poured their life’s passion into this mission.”

The two wings of Webb’s primary mirror had been folded to fit inside the nose cone of an Arianespace Ariane 5 rocket prior to launch.

After more than a week of other critical spacecraft deployments, the Webb team began remotely unfolding the hexagonal segments of the primary mirror, the largest ever launched into space. This was a multi-day process, with the first side deployed on 7 January and the second the day after.

JWST will now begin moving its 18 primary mirror segments to align the telescope optics. The ground team will command 126 actuators on the backsides of the segments to flex each mirror – an alignment that will take months to complete. Then the team will calibrate the science instruments prior to delivering Webb’s first images this summer.

Soon, JWST will also undergo a third mid-course correction burn – one of three planned to place the telescope precisely in orbit around the second Lagrange point, commonly known as L2, nearly 1 million miles from Earth.

This is Webb’s final orbital position, where its sunshield will protect it from light from the Sun, Earth, and Moon that could interfere with observations of infrared light.