The U.S. National Aeronautics and Space Administration launched the Upper Atmosphere Research Satellite 20 years ago this month. And now that bus-sized satellite is plunging toward Earth.
Mark Matney, an orbital debris scientist at the agency’s Johnson Space Center in Texas, says the craft will likely reenter the atmosphere on Friday. He says scientists will be able to narrow the time frame as it gets closer.
As far as where it will crash, Matney says the satellite passes over the Earth between 57 degrees north latitude and 57 degrees south latitude.
Everything from Canada down to the tip of South America, and from Siberia down to the tip of Africa and Australia could be where the satellite lands, said Matney.
Given that more than two-thirds of the planet is covered by water, space debris usually lands with a splash.
Still, there is the chance that the satellite could land with a thud, although Matney says this reentry is not cause for great concern.
“If you talk about the probability of you getting hit, it’s something like one in trillions, so actually the odds of you getting hit is quite small,” Matney says. “So, I don’t think anybody needs to be unduly concerned about it.”
The space agency says it has no reports of a person being injured or property being significantly damaged by reentering debris. But there was an incident in 1997.
“There actually was a lady in Oklahoma who was hit by a piece of very light debris from a reentering satellite, but it didn’t hurt her. It was a piece of insulation. She was out jogging, and it hit her,” recalled Matney. “That same reentry dropped two tanks over Texas.”
Matney says debris reentry is a common occurrence, averaging about one piece per day, but that the pieces usually are small. But he says this will be the first time in 30 years that a U.S. space agency satellite of this size will have crashed back to Earth.
Even though officials at NASA and the Department of Defense cannot yet provide a precise landing footprint, Matney says the science of figuring out what will land is exacting.
“We actually take time to get the original specifications, to get the different parts of the spacecraft, the material types, their shape, their mass,” explains Matney. “And we actually have computer programs that model the dynamics as it begins to heat up and break up and look at the temperatures those pieces reach and whether they reach the melting point of the metal.”
For instance, he says that because of aluminum’s relatively low melting temperature, aluminum objects usually disintegrate before they reach the surface of the Earth.
The agency expects 26 potentially hazardous pieces of this satellite to reach the ground, most of them made of titanium, stainless steel or beryllium, which have high melting points. These pieces of debris include batteries, wheel rims and empty fuel tanks. Debris is expected to range in mass from 0.6 to 158 kilograms.