A European space satellite that has been mapping the Earth’s gravitational field is set to crash down to Earth in the coming days, and it could provide a “real treat” for space watchers.
But could GOCE (pronounced “GO-chay”), which is set to make an “uncontrolled entry” into the atmosphere, present a risk to anyone on the ground?
“For the most part, these uncontrolled re-entries are the norm,” Space.com’s Tariq Malik told Yahoo News in a phone interview. “It’s not so much that we’ve been lucky to not get hit by one as it is the planet is so big.”
The European Space Agency does not know exactly when GOCE, short for Gravity field and steady-state Ocean Circulation Explorer, will crash to Earth, and experts there don't know exactly where it will land. But the general consensus is that it will re-enter Earth’s atmosphere sometime between Friday and Monday.
“It’s rather hard to predict where the spacecraft will re-enter and impact,” the ESA’s Rune Floberghagen told the New York Times. “Concretely our best engineering prediction is now for a re-entry on Sunday, with a possibility for it slipping into early Monday.”
And if all goes well, people may be able to watch the satellite safely enter the atmosphere and explode into a fireball of smaller fragments.
“The one thing I’m really wondering about is where the re-entry might be visible from,” Malik said. “It’s very instructive to watch this stuff burn up. From the ground, it’s like watching a giant fireball. If that happens, viewers on the ground could really get a treat.”
So far, the odds have worked out incredibly well for people on Earth. No known satellite has ever impacted a person or destroyed a significant piece of property. However, that doesn’t mean space junk hasn’t come close to civilization before. In 1979, fragments from the first U.S. space station SKYLAB landed in Western Australia, though no one was hurt in the impact. And in 2004, NASA’s Genesis satellite crashed into the desert in Utah when its parachute failed to deploy on re-entry. And again, even though the impact created a crater, no person or private property was harmed by the impact.
And it was estimated last year that ENVISAT, the largest satellite in history, could pose a 150-year threat to Earth. Having run out of fuel, no one knows when the 17,636-pound satellite will return to Earth and what kind of impact it might have.
Malik says that within about 24 hours of GOCE’s re-entry observers should have an accurate estimate of when it will enter the atmosphere. Then, within about 12 hours of its re-entry, scientists will begin to more closely predict where fragments from the satellite will land.
“It will start off as wide as a continent or an ocean,” Malik said. “By the end, nearly all of the possible trajectory lines will have been eliminated and they’ll have a good idea of where it’s headed.”
But even though it’s extremely unlikely that GOCE will pose a risk upon re-entry, Malik still says any would-be collectors would be wise to leave any found debris alone.
“It’s not really wise to touch it, even though it’s fallen down from space,” he said. “It was powered by an engine and you don’t know what kind of chemicals or residue are in there.”
- European Space Agency