The next six months will involve a series of careful maneuvers for Webb—some automated, others manual—that will test the nerves of everyone involved. NASA is accustomed to deploying rigid pieces of hardware, not floppy contraptions like Webb’s sun shield, which must fully expand so the telescope can cool down to very frigid temperatures. The observatory’s instruments don’t stand a chance without the sun shield, but they can also snag the cover as it opens. Engineers have spent years developing all kinds of contingency plans, including shimmying the observatory around if something gets stuck and needs a jolt. “You convince yourself that Hey, I’ve done everything humanly possible,” Mike Menzel, the Webb mission’s lead systems engineer at NASA, told me earlier this month. “There’s a lot of bad things that can happen. But all the things that I could plan for, I have planned for.” If one of those bad things does happen and it can’t be fixed, even with the perfect shimmy, years of work could be undone in an instant.

Unlike Hubble, Webb wasn’t designed with future repair missions in mind. Astronauts can’t fly to Webb to make any fixes, as they’ve done on four occasions for the other telescope. When the observatory runs out of fuel more than 10 years from now, its watch over the universe will end. Future robotic spacecraft could, in theory, sidle up to Webb, open its gas cap, and refuel it. Thomas Zurbuchen, NASA’s associate administrator for science missions, declared publicly for the first time yesterday that if Webb works, the agency will devote resources to achieving that future. “I’m going to put all the effort toward developing that technology,” Zurbuchen said. But “I am not going to start putting money into it before we’re there,” he told me.