NASA's James Webb Telescope Opens Mirror on Earth for Last Time Before Orbiting the Sun

The primary mirror of NASA's next generation James Webb Space Telescope (JWST) opened for the last time on Earth before the expected launch of the observatory on October 31, 2021.

As one of the final tests before the telescope is blasted into space aboard an Ariane 5 rocket from French Guiana in South America, engineers commanded the mirror to fully expand and lock itself into place, just like it will do once in orbit around the sun. The telescope will orbit the sun around a million miles away from Earth.

The successful completion of the test marks a key milestone in the lead up to the launch later this year. It was the last in a long series of checks that were designed to ensure that the telescope's primary mirror is ready to handle the telescope's long journey in space and a lifetime of discovery.

The primary mirror of the JWST, known as the Optical Telescope Element, is comprised of 18 hexagonal mirror segments made of gold-plated beryllium—a steel-gray metal. In total, this mirror measures 21-feet and four-inches in diameter—significantly larger than that of the pioneering Hubble Space Telescope, which JWST is intended to succeed.

The Optical Telescope Element will allow the JWST to observe the universe in a lower frequency range than Hubble, enabling it to view objects that are older and more distant.

"The primary mirror is a technological marvel," Lee Feinberg, optical telescope element manager for the JWST at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. "The lightweight mirrors, coatings, actuators and mechanisms, electronics and thermal blankets when fully deployed form a single precise mirror that is truly remarkable.

"This is not just the final deployment test sequence that the team has pulled off to prepare Webb for a life in space, but it means when we finish, that the primary mirror will be locked in place for launch. It's humbling to think about the hundreds of dedicated people across the entire country who worked so hard to design and build the primary mirror, and now to know launch is so close."

The James Webb telescope, developed by NASA in collaboration with the European Space Agency and Canadian Space Agency, will be the world's largest and most powerful space observatory once it is deployed.

The telescope will be able to conduct unprecedented observations that will cast new light on our solar system and distant exoplanets orbiting far away stars, as well as the mysterious structures and origins of our universe.

Engineers still need to conduct a few more tests before the launch of the telescope. These include extending and re-stowing two radiator systems that help to keep the observatory cool enough to carry out observations in the infrared frequency range.

Ritva Keski-Kuha, deputy optical telescope element manager for JWST at Goddard, said in a statement: "Pioneering space observatories like Webb only come to fruition when dedicated individuals work together to surmount the challenge of building something that has never been done before.

"I am especially proud of our teams that built Webb's mirrors, and the complex back-end electronics and software that will empower it to see deep into space with extreme precision. The completion of this last test on its mirrors is especially exciting because of how close we are to launch later this year."

James Webb Space Telescope's primary mirror
The telescope's primary mirror undergoing checks at NASA's Goddard Space Flight Center. NASA/Chris Gunn