China's first-ever space lab will be returning to Earth in late 2017, and "most parts" of the spacecraft will burn up on re-entry, the country's space program announced last week.
The news came after months of speculation that China had lost control of the Tiangong-1, or "Heavenly Palace-1," the space lab that was launched in 2011 with great fanfare.
In June, a satellite tracker named Thomas Dorman told Space.com that his observations suggested Tiangong-1 is in a "slow roll," with solar panels in an incorrect orientation, and is on track for an uncontrolled fall out of orbit.
"If I am right, China will wait until the last minute to let the world know it has a problem," he said.
China's Xinhua state news agency reported on the news of the pending re-entry of the spacecraft without indicating whether the space agency had lost control of the vehicle.
The space lab was originally meant to operate for two years, and its last manned mission was in 2013. It continued to gather data for several more years and then "ended its data service" this March, according to Xinhua.
It's not surprising for a defunct piece of spacecraft to fall back to Earth. The big question is howthe Tiangong-1 will return.
With China releasing few details about its space program in general or the status of the Tiangong-1 in particular, it's not clear whether the country will have the ability to steer the space lab as it hurtles toward Earth.
Before China announced the space lab's upcoming demise, one astrodynamicist told Space.com that even if the orbit was wonky, the world shouldn't rule out the possibility that China was able to steer the craft. Perhaps the space agency is choosing not to steer — possibly to save fuel — until it's almost time for re-entry.
More recently, astrophysicist John McDowell told The Guardian that in his eyes, China's announcement of the upcoming re-entry suggested the craft would be falling "naturally," without any human steering.
For small satellites, simply falling out of orbit is a fairly frequent occurrence.
For larger spacecraft — the Tiangong-1 is 34 feet long and weighs more than 18,000 pounds — it's rarer. That kind of uncontrolled re-entry tends to make headlines: You may remember NASA's Upper Atmosphere Research Satellite falling to Earth in in 2011 and the European GOCE satellite in 2013.
The Washington Post notes that the standard practice for larger spacecraft is, instead, a "planned descent":
"The wreckage that survives re-entry splashes down far from human habitation. Some 2,500 miles to the east of New Zealand, for instance, is a patch of the Pacific Ocean informally known as the spacecraft cemetery. Remains of the Mir station and more than a hundred other Russian, European and Japanese satellites sit in this area."
If the Tiangong-1's descent isn't controlled by humans, whatever survives re-entry will probably splash into the sea — the world is mostly ocean, after all. Even if it hits land, odds are low it would hurt anybody, both the Guardian and Space.com report. But there is a chance it could do damage, and it's hard to predict exactly where the debris might fall, McDowell told the newspaper.
Meanwhile, China has just launched the Tiangong-2 — the nation's second space lab, set to replace the Tiangong-1.
It's all part of a long-term project toward China's first fully functional, permanently staffed space station.
China is not part of the team of countries that cooperatively run the International Space Station.
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