BEIJING (AP) – It is expected that China's decommissioned and allegedly out-of-control Tiangong 1 space station will re-enter Earth's atmosphere sometime this weekend. It poses little risk to people and property on the ground, as most of the 8.5-tonne bus vehicle is burned upon re-entry into the city, although space agencies are not sure when and where that will happen  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 Space Agency predicts that the station will return to the atmosphere between Saturday mornings and Sunday afternoons – an estimate it calls "very variable," probably because it ever exists The changing shape of the upper atmosphere affects the speed of the objects falling into it.
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 is likely to be survived on reentry, especially its heavier components such as its engines. The likelihood that someone will be hit by rubble on Earth is considered less than one to one trillion.
Ren Guoqiang, spokesman for the Chinese Ministry of Defense, told reporters on Thursday that Beijing has informed the United Nations and the international community about Tiangongs 1 – entering through multiple channels.
HOW TOGETHER IS SPACE DEBRIS?
Debris from satellites, space launches and the International Space Station come into the atmosphere every few months, but it is known that only one of them was hit: an American Lottie Williams, who was training in 1997 An Oklahoma Park was hit by a falling piece of a US Delta II missile, but was not injured.
The most famous is the 77-ton Skylab from America, which broke through the atmosphere in 1979 and spread wreckage near the town of Perth in southwestern Australia, which seized the $ 400 for garbage.
The dissolution of the Columbia Space Shuttle in 2003 killed all seven astronauts and sent more than 80,000 pieces of debris to a large strip of the southern United States. No one on the ground was hurt.
In 2011, NASA's Osh atmosphere research satellite was considered a slight public risk when it came to Earth 20 years after its launch. Debris from the 6-ton satellite landed in the Pacific and did no damage.
China's own space program raised grave concern after it had used a rocket to destroy an out-of-service Chinese satellite in 2007, creating a large and potentially dangerous cloud
WHAT IS TIANGONG 1 AND WHAT IT WAS FOR IT USED?
Launched in 2011, Tiangong 1 was China's first space station to serve as an experimental platform for major projects such as the Tiangong 2, launched in September 2016, as a future permanent Chinese space station.
The station, whose name translates as "Heavenly Palace", housed 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 contact was interrupted in 2016. Since then, they are increasingly circling themselves 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 EXTENDS CHINA'S SPACE PROGRAM?
Since China's first manned mission in 2003 – after Russia and the US only the third country – has become increasingly ambitious projects, including the implementation a spacewalk and landing his jade rabbit rover on the moon.
China is now operating the Tiangong 2 spaceport facility, while the base station's 20-ton core module is expected to hit the market this year. The completed 60-tonne station is expected to go into operation in 2022 and run for at least ten years.
China was excluded from the 420-tonne International Space Station, mainly due to US legislation that prohibits such cooperation and concerns over the Chinese military's space communications program. China's space program is still 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 expected to start in 2020. China also plans to become the first country to land a probe on the other side of the moon.