The astronauts who just arrived at the Hubble Space Telescope are at an altitude with a higher-than-usual risk from flying space junk.
In fact, since reaching orbit, the astronauts' shuttle Atlantis has apparently already sustained a slight impact to one of its wings, and the agency is tracking another piece of debris that is expected to pass relatively near the spacecraft later today. The slight impact is not thought to have caused damage, and neither of these issues is of serious concern, NASA said.
While the astronauts are visiting Hubble, where they plan to complete five spacewalks to revamp the aging observatory, they will be exposed to greater potential impacts from orbiting trash than would be the case at other altitudes. Though a rogue screw or tiny satellite fragment may not seem like a big threat, when travelling at orbital speeds of about 20,000 mph, it can do a lot of damage.
The shuttle is at risk, too. If Atlantis were hit by space junk, the trash could easily puncture a hole in the ship that would render it unable to survive the trip home through the Earth's atmosphere. NASA has determined that this shuttle mission faces a 1-in-229 chance of a catastrophic debris impact.
That's more dangerous than a usual shuttle mission to the International Space Station, which orbits at a lower and less crowded altitude of 220 miles above Earth, compared to Hubble's lofty perch 350 miles high. The debris risk for a space station-bound mission is about 1 in 300.
NASA officials are confident the risk is manageable. And astronauts have said they accept the risk.
"We take it seriously, and we think we're in a position that it's acceptable to go fly," LeRoy Cain, deputy shuttle program manager, said a few weeks before launch.
In case emergency does strike, NASA has a detailed rescue plan already in place. A second space shuttle, Endeavour, is perched on a spare launch pad at NASA's Kennedy Space Center in Cape Canaveral, Fla., ready to lift off to save the spaceflyers if needed. A four-member backup crew has been training on the techniques that would be needed to rescue astronauts marooned at Hubble.
It would be a different problem were an astronaut on a spacewalk hit by roving debris. Though NASA's spacesuits are designed to shield astronauts from the harshness of space, they would have a tough time resisting a zooming piece of junk. If a hole was punctured in an astronaut's spacesuit, the air could leak out and the person could die if not rushed back into the pressurized space shuttle soon enough.
However, NASA says the chances of an impact strike this serious are very remote.
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