For the last couple of years, NASA’s next big space observatory — the James Webb Space Telescope — has been carefully pieced together at the agency’s Goddard Space Flight Center in Maryland. But now the telescope has left its primary home in the Northeast and has been delicately shipped to NASA’s Johnson Space Center in Houston, where the spacecraft will undergo extreme temperature testing to make sure it’s ready to be launched into deep space. It’s the first of a couple pit stops the telescope will make in the US before being shipped to South America for its scheduled launch in late 2018.

In truth, only part of the James Webb Space Telescope, or JWST, is in Houston right now. But it’s arguably the most crucial part: the telescope’s primary mirror. Comprised of 18 hexagonal segments of gold-coated beryllium, the mirror is what the JWST will use to gather light from the distant Universe, in order to study the earliest forming stars and galaxies. It spans over 21 feet in diameter, making it nearly six times larger in area than the mirror on NASA’s Hubble Space Telescope currently in orbit around Earth. It’s what makes the JWST the most powerful space telescope to date.

NASA needs to make sure that the spacecraft and its mirror will be able to handle launching to space

But before the telescope can start spying on galaxies, NASA needs to make sure that the spacecraft and its mirror will be able to handle the extreme conditions of launching to space. While at Goddard, the mirror underwent vibrational and acoustic testing, to simulate the movements the vehicle might experience during the initial rocket launch. Now in Houston, the mirror will go through cryogenic testing in a vacuum chamber, to simulate the extremely cold temperatures that the JWST will have to deal with at its final location — 1 million miles away from Earth.

To move the mirror to Johnson Space Center, the vehicle was carefully folded up inside a specialized shipping container and then loaded into a trailer truck. After an extra slow drive on the highway, the mirror was then stored inside an Air Force plane and flown to Houston. Another truck brought JWST to the space flight center, where the telescope was placed inside one of the agency’s clean rooms. Now, NASA is going to start preparing the telescope for a big cryogenic test that’s supposed to last up to 100 days. The test will occur in the same vacuum chamber that NASA used to test out the Apollo spacecraft that went to the Moon.

JWST will make its next stop in Redondo Beach, California

Once cryogenic testing is complete, JWST will make its next stop in Redondo Beach, California, at the headquarters of Northrop Grumman Aerospace Systems. Northrop has been the primary contractor for the telescope, and it will do the final assembly of the spacecraft — connecting the mirror to the sunshield that will protect the vehicle from too much heating from the Sun. JWST will do even more testing in California, before finally getting on a boat to its launch site in French Guiana. It’s there that JWST is supposed to launch on top of a European Ariane 5 rocket in October 2018.

But once the telescope launches, the stress is far from over. JWST is way too big to launch as is, so the telescope has to go into space folded up. Once it is deployed into space by the Ariane 5, the telescope will start to slowly unfurl as it makes its way to its destination. It’s a process that will take up to two weeks to complete, and a full month before JWST is at its final orbit.