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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