What will happen and how great is the risk?

The European Space Agency predicts the station reentered the atmosphere between Saturday morning and yesterday afternoon - an estimate it calls ‘ highly variable’, likely because the ever- changing shape of the upper atmosphere affects the speed of objects falling into it.

The Chinese space agency’s latest estimate puts re- entry between Saturday and Wednesday.

Western space experts say they believe China has lost control of the station. China’s chief space laboratory designer Zhu Zongpeng has denied Tiangong was out of control, but hasn’t provided specifics on what, if anything, China is doing to guide the craft’s re- entry.

Based on Tiangong 1’ s orbit, it will come to Earth somewhere between latitudes of 43 degrees north and 43 degrees south, or roughly somewhere over most of the United States, China, Africa, southern Europe, Australia and South America. Out of range are Russia, Canada and northern Europe.

Based on its size, only about 10 per cent of the spacecraft will likely survive being burned up on re- entry, mainly its heavier components such as its engines. The chances of anyone person on Earth being hit by debris is considered less than one in a trillion.

Ren Guoqiang, China’s defence ministry spokesman, told reporters Thursday that Beijing has been briefing the United Nations and the international community about Tiangong 1’ s re- entry through multiple channels.

How common is man made space debris?

Debris from satellites, space launches and the International Space Station enters the atmosphere every few months, but only one person is known to have been hit by any of it: American woman Lottie Williams, who was struck but not injured by a falling piece of a U. S. Delta II rocket while exercising in an Oklahoma park in 1997.

Most famously, America’s 77- ton Skylab crashed through the atmosphere in 1979, spreading pieces of wreckage near the southwestern Australia city of Perth, which fined the US $ 400 ( Dh1,468) for littering.