What to Expect When You're Expecting a Satellite to Fall

Not to get all Chicken Little on anyone, but the European Space Agency’s satellite, the Gravity Field and Steady-State Ocean Circulation Explorer, or GOCE, is falling right out of the sky.

While still over a hundred miles up, the GOCE should come down either Sunday or Monday according to The New York Times, but no one is sure of exactly where or when. The satellite, which was mapping the Earth’s gravitational field, is orbiting the Earth longitudinally as the Earth spins beneath it, like some sort of Wheel of Fortune where the prize is a rain of bits of a one-ton spacecraft.

Still, there’s probably no need to hunker in your bunker. Even though 100 tons of space debris falls to Earth every year, no one has ever gotten hurt by any, and only one person has ever reported getting hit. To expand our sample size, an average of 111–235 tons of meteorites hit Earth each day, and so far there’s only been one confirmed case of someone getting hit with a meteor.

Fact is the Earth’s surface is 196.9 million square miles, so even lying down the odds are smaller than slim. It’s much more likely that like the Mir space station or NASA’s 6-ton Upper Atmosphere Research Satellite, GOCE is heading for a splashdown in the Pacific. As it gets closer to falling, scientists should be able to better predict where its debris will land.

But, for kicks, let’s say as GOCE’s fiery death approaches, the ESA says its headed for you, or at least your state. On a scale of blasé to fucking-in-the-streets, how panicked should you be?

Probably still not much. Rune Floberghagen, GOCE’s mission manager, told the Times that the debris will endanger about 15 to 20 square yards of the Earth’s surface. As they re-enter the atmosphere, most satellites break up and only 10-40 percent of the mass of the spacecraft usually makes it all the way down to the surface; only 25 percent of the GOCE is expected to reach the ground, so a total of 500 pounds. And even of that fraction will be in 25-45 smaller, light pieces, according to the ESA. The Times says a piece could be as big as 200 pounds.

Whatever reaches the ground may or may not be going Felix Baumgartner-like speeds. Lottie Williams is the aforementioned only person ever hit by space debris. In 1996, part of the fuel tank of a Delta II rocket re-entered the atmosphere and struck her on the shoulder. Did it scorch through her arm? Knock her down like a bullet from the blue? As she told Alec Liu, "I felt a tapping on my shoulder.”

The bit that hit her weighed about as much as a soda can, and lighter bits of space junk like that hit the Earth at usually around a moderate 18 miles per hour. Heavier bits, less susceptible to air resistance, can come down faster than 150 miles per hour.

Sure, 200 pounds falling from space could do some damage, so if the ESA calls you Sunday morning to tell you to stay off the roof for a few hours, you might as well listen. But given that the GOCE is a one-percent increase in stuff dropping out of the sky that day—a figurative and likely literal drop in the ocean—you might as well not worry about this, unless you also want to be worried all the time. You might as well feel flattered. At least call Lottie Williams afterwards.