New Zealand in path of China's out-of-control space station

A Long March 2FT1 rocket carrying Tiangong-1, China's first unmanned space module, blasts off on September 29, 2011. Tiangong-1 is now falling back to earth. Photo / Getty

An out-of-control space station put in orbit by China will come crashing back to the planet within weeks and could hit Europe, the US, Australia or New Zealand.

The Tiangong-1 space station, which is hurtling towards Earth carrying a "highly toxic chemical", will likely hit sometime between March 24 and April 19.

Agencies around the world have been monitoring the doomed 8.5-tonne craft, which is believed to contain dangerous hydrazine, as it falls toward the planet.

The flight path of Tiangong-1 shows where it crosses over New Zealand, putting the lower North Island-upper South Island in potential danger of falling debris. Image / Satflare

However, it will only be during the final week that experts will know with full confidence when it would land and where the debris will fall.

According to Aerospace, a research organisation that advises government and private enterprise on space flight, the space station will re-enter the Earth's atmosphere in the first week of April.

Exactly where it will hit is slightly harder to predict, although experts agree it will be somewhere between latitudes of 43° north and 43° south.

The chances of re-entry are slightly higher in northern states in the US, central Italy, northern Spain, northern China, New Zealand, the Middle East and parts of South Africa and southern Africa.

Scientists from the European Space Agency (ESA), based in Paris, are among those tracking Tiangong-1, which means 'heavenly palace'.

"Every couple of years something like this happens, but Tiangong-1 is big and dense so we need to keep an eye on it," Jonathan McDowell, an astrophysicist from Harvard University told the Guardian.

While most of it will burn up during re-entry, around 10 to 40 per cent of the satellite is expected to survive as debris, and some parts may contain dangerous hydrazine.

However, due to changing conditions in space, it is not possible to accurately predict where the module will land.

Image shows a 1:1 prototype of the China-made unmanned space module Tiangong-1. Photo / Getty

In recent months, the spacecraft has been speeding up and it is now falling by around 6km a week. In October it was falling at 1.5km a week.

ESA issued an updated prediction of its re-entry date on January 12, giving a current estimated window between March 17 and April 21.

"It is only in the final week or so that we are going to be able to start speaking about it with more confidence," said Dr McDowell.

"I would guess that a few pieces will survive re-entry. But we will only know where they are going to land after after the fact."

Website Satflare, which provides online 3D tracking of more than 15,000 satellites, has calculated what it thinks are the chances of the space station entering the atmosphere during the next three months.

According to its analysis of orbital elements gathered during the last months, the re-enter may occur in March (20 per cent), in April (60 per cent) or in May 2018 (20 per cent).

These predictions may also change as new orbital measurements will be available.

Aerospace Corp has also issued its own forecast.

In a written statement, a company spokesman said: "When considering the worst-case locations, the probability that a specific person will be struck by Tiangong-1 debris is about one million times smaller than the odds of winning the Powerball jackpot.

"In the history of spaceflight, no known person has ever been harmed by reentering space debris.

"Only one person has ever been recorded as being hit by a piece of space debris and, fortunately, she was not injured."

Aerospace Corp says Tiangong-1 will re-enter the planet's atmosphere in mid to late March, with wiggle room of two weeks either side of this timeframe. Image / Aerospace

On September 14, 2016, China made an official statement predicting Tiangong-1 would reenter the atmosphere in the latter half of 2017.

Experts from Aerospace's Center for Orbital and Reentry Debris Studies (Cords) have been studying the space station and in November updated their predictions for its uncontrolled re-entry.

The Tiangong-1 spacecraft launched in 2011, with the aim of using the craft to set up a larger space station.

The craft is now at an altitude of less than 300 kilometres (186 miles) in an orbit that is decaying, forcing it to make an uncontrolled re-entry.

Holger Krag, head of ESA's Space Debris Office, said: 'Owing to the geometry of the station's orbit, we can already exclude the possibility that any fragments will fall over any spot further north than 43°N or further south than 43°S.

"This means that re-entry may take place over any spot on Earth between these latitudes, which includes several European countries, for example.

"The date, time and geographic footprint of the re-entry can only be predicted with large uncertainties.

"Even shortly before re-entry, only a very large time and geographical window can be estimated."

Much of the spacecraft is expected to burn up in the atmosphere upon re-entry.

But owing to the station's mass and construction materials, there is a possibility that some portions of it will survive and reach the surface.