Parts of giant Nasa satellite to crash to Earth, posing low risk

Parts of a giant Nasa satellite will crash to Earth on Tuesday evening, the US space agency is warning – but the chance of being struck is extremely low.

According to the US military’s Space Force, the roughly 1,323lb (600kg) spacecraft, one of twin probes launched in 2012 to investigate the Van Allen radiation belt, is estimated to re-enter Earth’s atmosphere at about 7.45pm EDT.

Most of the craft, it said in a prediction published Monday, will burn up on re-entry, yet some components are expected to survive. There is a small chance, which the Space Force calculates at 1 in 4,200, that somebody on Earth could be harmed.

“Nasa and Space Force will continue to monitor the re-entry and update predictions,” the statement said, adding there was an initial uncertainty of plus or minus 24 hours in the calculations.

Debris falling from space is not uncommon, and Wired reported in 2009 that over a 40-year period roughly 5,400 tons are thought to have survived re-entry.

But the odds of being hit are low because about 71% of Earth’s surface is covered by water. A 2011 report by space.com said the overall chance of anybody being hurt was 1 in 3,200, and for any given individual far less. “The odds that you will be hit are one in several trillion, so quite low for any particular person,” Mark Matney, a scientist in the orbital debris program office at Nasa’s Johnson space center, Houston, told the outlet.

One not so lucky was Lottie Williams, a Tulsa, Oklahoma, resident who was walking through a park in January 1997 when she saw a sudden flash of flight, followed by a six-inch chunk of metal striking her on the shoulder.

The small, blackened fragment was never formally identified as space junk. But the time and location was confirmed by Nasa as consistent with the re-entry and break up of the second stage of a Delta rocket that had been orbiting for months. And Williams, who was not injured, remains the only person known to have been struck by falling manufactured space debris.

On Sunday, a chunk of meteor crashed through the roof of a house in Germany, one of an estimated 15,000-17,000 meteorites to reach Earth every year, although the majority end up on the floor of the ocean.

The Space Force advisory about Tuesday’s satellite crash, meanwhile, focuses more on where it came from than where or when it will land. The craft is Van Allen Probe A, launched with its twin, Van Allen Probe B, from Cape Canaveral, Florida, on 30 August 2012 on a mission to investigate the Van Allen belts of charged particles trapped by Earth’s magnetic field.

The probes were deactivated in 2019 when they ran out of fuel and were no longer able to orientate themselves towards the sun. Early calculations that they would reenter Earth’s atmosphere in 2034 proved inaccurate, although the second probe is not expected to return before the end of this decade.