China's decommissioned and allegedly out-of-control Tiangong 1
Below are some questions and answers about the station, its reentry and the past and future of China's ambitious space program
WHAT HAPPENS AND HOW BIG IS THE DANGER?
The European The Space Agency predicts that the station will re-enter the atmosphere between Saturday morning and Sunday afternoon – an estimate called "highly variable", probably because the ever-changing shape of the upper atmosphere reduces the speed of Influenced objects.
China Space Agency's most recent estimate is its re-entry between Saturday and Wednesday.
Western space experts say they believe China has lost control of the station. Zhu Zongpeng, China's Chief Space Laboratory, denied that Tiangong was out of control, but did not specify what China would do to control the ship's re-entry.
Based on the orbit of Tiangong 1, it will come to Earth somewhere between latitudes 43 degrees North and 43 degrees South, or about anywhere over most of the United States, China, Africa, Southern Europe, Australia and South America. Out of reach are Russia, Canada and Northern Europe.
Due to its size, only about 10 percent of the spacecraft will probably be survived on reentry, especially the heavier components such as the engines. The likelihood that someone will be hit by rubble on Earth is considered less than one to one trillion.
Ren Guoqiang, Chinese Ministry of Defense spokesman, told reporters on Thursday that Beijing has informed the United Nations and the international community about Tiangongs 1
HOW TOGETHER IS MAN-MADE SPACE DEBRIS?
Debris from satellites, space launches, and the International Space Station enter the atmosphere every few months, but only one person is known American Lottie Williams, who struck in 1997 during a sport in an Oklahoma Park from a falling piece of a US delta II missile hit, but was not injured.
The best known is that America's 77-tonne Skylab crashed through the atmosphere in 1979, spreading wreckage near the southwestern city of Perth, which seized $ 400 for garbage.
The separation of Columbia Space Shuttle in 2003 killed all seven astronauts and sent more than 80,000 debris on a large strip of southern United States. No one on the ground was injured.
In 2011, the NASA Atmospheric Research Satellite was considered a slight public risk when it came to Earth 20 years after its launch. Wreckage of the 6-ton satellite landed in the Pacific Ocean and caused no damage.
China's own space program was a source of concern after a missile killing an out-of-service Chinese satellite in 2007 and a potentially dangerous debris cloud.
WHAT IS TIANGONG 1 AND WHAT IT HAS BEEN USED FOR?
Tiangong 1 was launched in 2011 and was China's first space station. It served as an experimental platform for major projects such as the Tiangong 2 launched in September 2016 and a future base station Chinese Space Station
The station, whose name translates as "Heavenly Palace", hosted two manned missions that included China's first female astronaut and served as a test platform for perfecting docking and other operations. The last crew left in 2013 and the contact was interrupted in 2016. Since then, it has been increasingly observed from Earth while being monitored.
The station had two modules, one for their solar cells and motors, and one for an astronaut couple to live in and perform experiments. A third astronaut slept in the Shenzhou spacecraft docking at the station, which also included personal hygiene and food preparation facilities.
HOW ADVANCED IS CHINA'S SPACE PROGRAM?
Since China launched its first manned mission in 2003 – after Russia and the US only the third – it has been embarking on increasingly ambitious projects, including a spacewalk and landing its Jade Rabbit Rover on the Moon
China is now operating the precursor space station Tiangong 2, while the 20 ton core module of the permanent station is due to be launched this year. The completed 60-tonne station is expected to be commissioned in 2022 and operated for at least ten years.
China was excluded from the 420-tonne International Space Station, mainly due to US legislation that prevented such cooperation and concerns over the strong military ties of the Chinese space program. China's space program remains very secretive and some experts have complained that a lack of information about Tiangong 1's design makes it harder to predict what might happen when it rejoins.
A mission to land another rover on Mars and bring back samples is scheduled to start in 2020. China also plans to become the first country to land a probe on the other side of the moon.
China is to recruit civilian astronauts, reinforce manned missions
Official website of China manned space: en.cmse.gov.cn/col/col1763/index.html