In May, Webb was packed into a shipping container and flown on a C-5 military transport plane to NASA’s sprawling facility in Texas, the Johnson Space Center. Engineers dipped the telescope into a massive cryogenic testing chamber that exposed the hardware to the frigid temperatures of space. The telescope survived the test, as well as the devastating wrath of Hurricane Harvey, which flooded the streets of Houston and forced some of Webb’s guardians to hunker down and sleep in offices or conference rooms at Johnson until the storm passed.

Webb will eventually be flown to California, where it will receive its sun shield and spacecraft hardware and undergo still more tests. When its many parts are finally assembled, Webb will be too massive to transport by plane, so it will sail by ship to French Guiana. There, it will take off from a European-operated launch facility, aboard an Ariane 5 rocket built by the European Space Agency. The Ariane fleet recently sparked some readiness concerns of its own when a rocket launched its payload, two communications satellites, into the wrong orbits. NASA has joined the European Space Agency in its investigation of the anomaly. The agencies have a full year to troubleshoot and implement fixes, but there’s no doubt the situation has rattled the nerves of the Webb team.

The GAO report starts out by praising the Webb mission for making “considerable progress” in the last few months in hardware integration, but things go downhill from there.

The GAO places blame on Northrop Grumman for delays. “For several years, the prime contractor has overestimated workforce reductions, and technical challenges have prevented these planned reductions, necessitating the use of cost reserves,” the report said. Northrop Grumman did not respond to a request for comment about this assessment.

GAO says Northrop Grumman ate up three months of reserve time “due to lessons learned from conducting deployment exercises of the spacecraft element and sun shield,” but doesn’t say what those are.

This sounds particularly ominous when you consider just how complicated Webb’s deployment process is going to be. When the telescope launches, Webb will be folded up like a flower before spring. As it travels to its orbit around the sun, Webb will spend about two weeks blooming, unfurling solar arrays, antennas, the sun shield, and other components, all the while making course corrections so it ends up in the right place. The automated process involves about 180 deployments. Very, very little can go wrong. NASA officials have said Webb can only withstand the failure of about six steps in this sequence. If the telescope experiences a glitch that prevents it from opening up completely, it will become just another piece of abandoned space junk. Unlike Hubble, the Webb is not designed to received repair crews, and at nearly 1 million miles from Earth, it’s too far for astronauts to reach with current U.S. spaceflight technology.