And indeed, U.S. Space Command cataloged two objects from Sunday’s launch, one being Wentien and the other the discarded core stage. Astronomer Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics expects the stage to reenter Earth’s atmosphere within a week or so.

“Unfortunately we can’t predict when or where,” he explained to me in an email. “Such a large rocket stage should not be left in orbit to make an uncontrolled reentry; the risk to the public is not huge, but it is larger than I am comfortable with.”

During a livestream of the launch on China Global Television Network, Xu Yangson, director general of the Asia-Pacific Space Cooperation Organization, said China took measures this time to make sure that the core stage will come back down in a controlled manner, but did not elaborate. When I asked about Xu’s comment, McDowell said: “I think he is misinformed.” McDowell is likely correct, as the Long March 5B core stage would require a significant upgrade or revision to suddenly have the capacity for controlled reentry.


As for the Wentien module, it will now be used to support a host of scientific experiments ranging from microgravity studies and the effects of space radiation through to experiments to study the growth of plants, insects, small mammals, and microbes. A third module, named Mengtian, is scheduled to launch in October. China intends to use its Tiangong space station for 10 years, during which astronauts will work for stints lasting six months.

More: Damaged SpaceX Rocket Delays NASA’s Next Astronaut Mission.