Update: On January 7, 2018 at 8pm EST, SpaceX successfully launched the Zuma mission and landed its Falcon 9 rocket back on Earth. The launch marks the company's first mission of 2018, and its 21st successful rocket landing.

Usually, when a SpaceX thing unexpectedly goes boom, it grounds the company for months and raises questions about safety and reliability. On Sunday, November 5, SpaceX was preparing for an experimental engine test at its facility in McGregor, Texas when a propellant leak ignited, damaging the test stand.

But despite the explosion, Elon Musk’s spaceflight company will push on with its planned launches uninterrupted. The first mission following the failure will fire off on Thursday night from Kennedy Space Center during a two-hour window opening at 8pm Eastern time—and it’s a notable one. The payload, codenamed Zuma, is yet another covert mission for the US government. And this one is even more hush-hush than before, squeezed into the end of SpaceX’s 2017 launch slate with just a month’s public notice.

Veteran aerospace manufacturer Northrop Grumman built the payload, according to a document obtained by WIRED and later confirmed by the company. The company says it built Zuma for the US government, and it’s also providing an adapter to mate Zuma with SpaceX’s Falcon 9 rocket. But that’s where information starts tapering off. A typical SpaceX mission on the manifest would tell you exactly what the payload is and where it’s being delivered. Northrop Grumman simply says Zuma is bound for low-Earth orbit—or a destination between 100 and 1,200 miles above Earth’s surface.

At NASA’s Kennedy Space Center, mission payloads have three levels of security restrictions for pre-launch processing. Zuma is categorized at the highest level, sharing the designation with two other SpaceX payloads this year: the secretive X-37B spaceplane, launched for the Air Force, and a clandestine surveillance satellite for the National Reconnaissance Office. Northrop Grumman acknowledges that its payload—the documents obtained by WIRED mention that it is a satellite—was built for the government, but it did not specify which branch.

Weirdly, Northrop Grumman will be a direct competitor to SpaceX come July, when the company will complete the acquisition of spaceflight company Orbital ATK, which also delivers cargo to the International Space Station for NASA. Regardless, Northrop praises SpaceX’s prices and reliability; Zuma’s launch date was crucial to the success of the payload, and while the public acknowledgement only came in October, Northrop established a rigid November launch slot with SpaceX earlier this year. “This event represents a cost-effective approach to space access for government missions,” says Lon Rains, communications director for Northrop Grumman. “As a company, Northrop Grumman realizes that this is a monumental responsibility and has taken great care to ensure the most affordable and lowest risk scenario for Zuma.” Such praise from an old-school space systems company (and especially a future competitor) is pretty rare, especially for SpaceX.