NASA Satellite Expected To Collide With Earth

According to NASA, a retired U.S. research satellite the size of a school bus has been sucked into the Earth's gravitational pull. The space agency expects the satellite to break into pieces on entry to the atmosphere, and for some of those pieces — some as heavy as 300 pounds — to rain down later this week. Donald Kessler, who served as NASA's senior scientist for orbital debris research, tells Michele Norris that an event of this nature is highly unusual — and odds are slim that the debris will injure people or destroy property.

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MICHELE NORRIS, host: According to NASA, a retired U.S. research satellite has been sucked into the Earth's gravitational pull. The space agency believes it will break apart, and pieces of it will crash into the planet later this week. But where and when exactly, they don't yet know.

Now, space junk falls to Earth on an almost daily basis without injuring people or property. But this piece of falling space junk is far bigger than the norm. It's 1,300 pounds, the size of a school bus.

Donald Kessler spent more than 30 years with NASA, most recently as the agency's senior scientist for orbital debris research. And he joins me now to talk about a particular piece of orbital debris. Welcome to the program.

Dr. DONALD KESSLER: Thank you.

NORRIS: When was the last time a spacecraft of this size crashed into Earth?

KESSLER: Well, it has been a while but things re-enter almost every day and most of it does burn up. And there have been within the last year several objects that have survived re-entry. And people have found those objects and displayed them. You can usually find them on the Web. There are pictures of things that have survived re-entry.

NORRIS: And when they land they just arrive with a thud in someone's farm field?

KESSLER: That's exactly what happened, though. It was around February of this year when a person in Wyoming was walking out in his field and heard a thud, and eventually found this cylinder that was about 20 inches in diameter in a crater. It turned out to be a piece of Russian spacecraft. And it's the type of things that usually survive re-entry.

Things that are made out of titanium or stainless steel, beryllium, that all have high temperatures for melting, survive re-entry. But usually most everything else burns up.

NORRIS: So, tell us a little bit more about this research satellite. What will likely happen when it re-enters the atmosphere?

KESSLER: Well, it will start to break up is the first thing that will happen to it because the outer skin will not be able to withstand the heat and the forces of re-entry. And as it breaks up, it'll start releasing various pieces of it. And most of those pieces will just totally disintegrate and not survive to the ground. But there'll be...

NORRIS: Most.

KESSLER: Yes. There will definitely be at least a handful of pieces that it will survive and land somewhere, and could be found if it happened to land on land.

NORRIS: And there's a handful, not literally a handful, not something that'll fit in your hand. So this will actually probably be quite large, right?

KESSLER: Yeah, one piece may be as large as 300 pounds.

NORRIS: Now, we don't want to freak people out, you know? And we certainly don't want to send people into a panic. But what's the likelihood that this could actually fall on a person or a building or actually strike someone or something?

KESSLER: Well, the calculated risk is 1 in 3,800 that somebody would be injured on the Earth. And since there are literally billions of people on Earth, the chances that it be either be you or me is something like one chance and 10 trillion.

NORRIS: I have one small, last question for that farmer who found that debris in his field. If this lands someplace on open land, who owns that piece of debris?

KESSLER: The person who put it in orbit. Any time you launch something into space, the launching nation is responsible for that no matter what happens. And for that reason, there is a lot of responsibility then placed on the people who put things in space. And so, if they cause an injury, they are liable for it.

NORRIS: So that lands in your backyard, if this lands on your backyard, you can't put it on eBay.

KESSLER: Well, you probably could because they would bother to ask for it.

NORRIS: Oh, okay. Maybe you shouldn't put it on eBay.

(SOUNDBITE OF LAUGHTER)

KESSLER: Right, at least not without permission.

NORRIS: Donald Kessler spent more than 30 years with NASA. He was most recently the agency's senior scientist for orbital debris research. Donald Kessler, thank you very much.

KESSLER: You're welcome.

(SOUNDBITE OF MUSIC)

NORRIS: More coming up on ALL THINGS CONSIDERED.

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