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NASA

Falling satellite could hit Sweden: experts

A 20-year-old satellite that has fallen out of orbit is expected to plunge back to Earth sometime next week and its projected landfall could strike Sweden, according to NASA experts.

An out of use 6.5-tonne Upper Atmosphere Research Satellite, known in the science circles as UARS, is expected to fall from orbit late next week and it could strike Sweden.

While most of the satellite is expected to burn up after it re-enters Earth’s atmosphere, NASA projects that about 545 kilogrammes of pieces will survive and plunge somewhere on the globe spanning a 500-mile radius.

Experts cannot forecast the exact locations of landfall, but based on the satellite’s current orbit and inclination, the strike zone is calculated to be somewhere between 57 degrees north and 57 degrees south of the equator, according to NASA.

Sweden extends between the 55th and 69th northern latitudes, which theoretically puts everything south of Gothenburg at risk, but NASA experts say the risk is considered minimal and calculate that it is a 1-in-3,200 chance that piece would actually hit a person.

The likely strike zone is a worldwide swath that covers most of the planet’s six inhabited continents and three oceans.

Since the dawn of the 1950s Space Age, there have been no confirmed reports of injury from re-entering space objects.

UARS, which ran out of gas in 2005, was originally deployed in 1991 from the Discovery space shuttle.

Its nearly 5 billion kronor ($750 million) mission was to study Earth’s atmosphere and its interactions with the sun by measuring the concentrations and distributions of gases vital to ozone depletion, climate change and other atmospheric phenomena.

According to NASA, readings from the satellite provided conclusive evidence that human-produced chlorofluorcarbons released into the atmosphere is the root cause of the polar ozone hole.

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Italian astronaut safe after space alert: Nasa

Italian austronaut Samantha Cristoforetti is "safe and doing well" at the International Space Station after an alert sounded on Wednesday that could indicate a dangerous ammonia leak, but may have been a false alarm, the US space agency said.

Italian astronaut safe after space alert: Nasa
Italian Samantha Cristoforetti is one of six astronauts currently at the International Space Station. Photo: Kirill Kudryavtsev/AFP

Cristoforetti and five other crew members donned emergency masks and hurried to the Russian side of the orbiting lab after the alert at around 10.00am (Rome time), closing the hatch to the US side behind them.

While the Russian space agency told news outlets in Moscow that the cause was a toxic ammonia leak, Nasa said there was no data to confirm that, and stressed that the crew was safe. Ammonia is used in the cooling and heating systems at the orbiting outpost.

Nasa suspects that a “false indication” is at the root of the problem said Jim Kelly of mission control in Houston, Texas, speaking to US astronaut and space station commander Barry Wilmore in an exchange broadcast on Nasa television.

“Big picture perspective, we are still trying to figure out exactly what happened. We are not entirely convinced that this is an ammonia leak,” Kelly said. A sensor problem or a computer relay issue could have led to the alarm, he added.

“It is becoming a stronger case that this is a false indication, which is great news,” Kelly said.

The six astronauts taking shelter in the Russian segment have enough food for at least a week, Nasa said.

“Hey everybody, thanks for your concern. We're all safe & doing well in the Russian segment,” Cristoforetti said on Twitter.

Problem in loop

The problem became apparent when flight controllers in Houston “saw an increase in pressure in the station's water loop for thermal control system B then later saw a cabin pressure increase that could be indicative of an ammonia leak in the worst case scenario,” Nasa said on its website.

Russia's space agency blamed the evacuation on a leak of a “toxic substance was emitted from a cooling system into the station's atmosphere” in the US segment of the station, the agency said in a statement. A representative of the Russian mission control center told Russian news agencies that the substance was ammonia.

The International Space Station (ISS) is a rare area of US-Russian cooperation that has not been hit by the crisis in Ukraine, which has prompted Washington to impose sanctions on Moscow. In total 16 countries work on the ISS, whose cost is mainly shouldered by the United States.

Since Nasa phased out the space shuttle system in 2011, it depends entirely on Russia to send its astronauts to the ISS.

The Expedition 42 crew had been awake for about two hours before the alarm sounded, and was at work unloading the SpaceX Dragon cargo carrier which arrived days ago with more than 2.5 tons of supplies and science experiments.

Two women and four men are on board the space station, making up a crew that hails from Russia, the United States and Italy. They include Wilmore, Cristoforetti, Elena Serova, Alexander Samoukutyaev, Terry Virts and Anton Shkaplerov.

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