On Monday, the agency announced the James Webb Space Telescope — a 43.5-foot long telescope with a 21-foot diameter mirror — was opened for the last time on Earth, letting its foldable mirrors be fully extended in their shimmering glory.
It’s one of the last checkpoints on the way to an October 31, 2021 launch for the telescope.
“It has been very interesting, and extremely rewarding to see it all come together,” Ritva Keski-Kuha, deputy optical telescope element manager for Webb at Goddard, says in a press statement. “ The completion of this last test on its mirrors is especially exciting because of how close we are to launch later this year.”
During the final test, the telescope’s primary mirror — at 21.4 feet long, it’s about the size of George Washington’s nose on Mount Rushmore — was instructed to fully expand and lock itself into place. In an attempt to make the testing conditions as similar to space as possible, special gravity offsetting equipment was attached to the telescope.
Watch NASA put the telescope’s mirrors through a string of tests.
“The lightweight mirrors, coatings, actuators and mechanisms, electronics and thermal blankets when fully deployed form a single precise mirror that is truly remarkable,” said Lee Feinberg, optical telescope element manager for Webb at NASA's Goddard Space Flight Center, on Monday.
“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.”
Is James Webb Much better than Hubble?
The road getting here wasn’t always easy. The telescope was conceived in the 1990s as the next in line to Hubble, with a primary mirror around seven feet.
But Hubble had a luxury Webb won’t: It was designed to be serviced, meaning if something went wrong, astronauts could travel up to its 340-miles-above-Earth perch and repair it. Hubble saw five servicing missions and was even launched aboard a space shuttle in 1990.
But Webb won’t be a few hundred miles above Earth. It will be at Lagrange point 2, or L2, a gravitationally stable point a million miles from Earth where JWST will orbit the Sun.
Because of its massive size, Webb will also have to be folded up in an Ariane rocket launched from the European Space Agency’s French Guiana Space Center and follow a sequence of commands to unfurl. If it fails to do this, NASA will be out to the tune of $10 billion dollars — or about four Curiosity rovers.
This has made getting it right critical, and lead to a series of delays. In fact, the mission was nearly canceled in 2011 because of cost overruns. It has had five launch dates in all:
- October 2018
- “Early 2019” because of construction delays
- A delay to no sooner than May 2020 after it failed some hardware tests
- A solid date of March 30, 2021, set by then-NASA administrator Jim Bridenstine in 2018
- A final launch date later this year on Halloween due to technical issues and Covid-19 related setbacks
What can the James Webb telescope do?
Once it gets to space, it should all be worth it. The telescope will have capabilities far surpassing that of Hubble. Beyond having a mirror six times larger than Hubble, it will also have deeper infrared capabilities than its ancestor telescope. It will be able to:
- Look to the early universe for the first large galaxies
- Peer into the atmospheres of exoplanets as they pass in front of their home star, letting us know if any have the same composition as Earth’s
- Take direct images of exoplanets
- Look at stars and planets as they form
- Make detailed observations of the outer planets and their moons, as well as objects in the Kuiper Belt like Pluto
- Measure the effects of dark matter and dark energy
- Watch galaxies form
If it’s successful, it will radically transform our understanding of the universe and give us insight into the biggest questions in astronomy.
And if it doesn’t we don’t have a Plan B ready to go.