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NASA engineers are getting one last look at the James Webb Space Telescope (JWST): a final test to show that its 18 gold-tinted mirror segments can unfold into a precise honeycomb configuration. After the test concludes this week, the giant instrument will be folded up, packed into a shipping container, and shipped off to French Guiana, where it will launch into space on 31 October.

The 6.5-meter-wide JWST is the agency’s next great observatory, the successor to the Hubble Space Telescope. In a NASA briefing today, Program Scientist Eric Smith told reporters it was born out of a realization in the mid-1990s that, no matter how long it stared into deep space, Hubble would never be able to see the universe’s very first stars and galaxies and learn how they formed and evolved. The expanding universe has “redshifted” the light of those primordial objects out of the visible spectrum; NASA needed a space telescope that worked in the infrared. “So the idea of Webb was born,” Smith says. Since then, astronomers have discovered thousands of exoplanets. Smith says JWST will be able to probe their atmospheres for molecules such as carbon dioxide, water, methane, and others that could suggest the presence of life.

Getting the $9 billion contraption to the point of departure has taken NASA much more time and money than it or Congress ever suspected. The construction of JWST proved to be the most complex and difficult science project in the agency’s history. The process of testing the telescope’s folding mirror, multilayered sunshield, and cryogenically cooled instruments has stretched years longer than planned.

But come late August, all that will be over as JWST, in a protective cocoon, will be taken from Northrop Grumman’s facility in Redondo Beach, California, and put onto a ship. The telescope will sail through the Panama Canal to Europe’s spaceport near Kourou. Unlike the 2.4-meter-wide Hubble, which fit comfortably inside the bay of the Space Shuttle, JWST’s mirror is much larger than the fairing on top of an Ariane 5 rocket, so it is elaborately folded to fit inside it.

Following launch, JWST will embark on a 6-month journey to its station at a gravitational balance point far beyond the Moon’s orbit. A few days after launch, engineers will begin the long and delicate process of deploying all the folded parts of the craft, aligning and focusing the 18 segments of the main mirror, cooling the instruments, and checking that everything works. The process is mapped out “hour by hour and day by day,” said NASA Instrument Systems Engineer Begoña Vila.

JWST’s first year of operation is also fully mapped out, said project scientist Klaus Pontoppidan of the Space Telescope Science Institute, with observing time awarded to researchers from 44 countries as well as 45 U.S. states plus Washington, D.C., and the U.S. Virgin Islands. “It was not only built to do what Hubble did,” Pontoppidan said, “but to answer questions that can’t be done any other way.”