Space junk could hinder Hubble repair mission

HOUSTON -- The shuttle that will carry astronauts into space next month to repair the Hubble Space Telescope faces a greater risk than usual of a catastrophic collision with space debris, NASA officials said Monday.

The risk of a fatal accident exceeds a NASA safety standard. As a result, NASA chief Michael Griffin will be involved in the final decision to launch, which is scheduled for Oct. 10, said shuttle program manager John Shannon.

The Hubble mission requires the shuttle to go into a higher orbit than a trip to the International Space Station. There's more space debris at that elevation, Shannon said.

"We've had some vehicle breakups on orbit, and they have made the (debris) environment worse," he said.

Shannon did not specify what led to the extra risk for the Hubble mission. Two incidents in 2007 led to the biggest jump in space debris in decades:

• China shot an aging satellite out of orbit, creating a vast field of fragments.

• An old Russian rocket circling the Earth exploded in what a NASA space-debris newsletter called a "very serious" accident.

The Pentagon shot down a failed military satellite this year, but NASA and Pentagon officials said the debris that was created posed no risk to the space shuttle and quickly tumbled out of orbit.

Even a tiny rock or shard of metal in space can inflict serious damage to a spacecraft, because debris in orbit is traveling thousands of miles per hour.

The biggest worry on the shuttle is the brittle material that shields the ship's nose and wings from high temperatures upon re-entry into the Earth's atmosphere.

In the past five years, the shuttles have spent most of their time in space at the space station, which partially surrounds the spaceships and shields them from debris. Shuttle Atlantis will have no such protection on its mission to fix and upgrade the Hubble.

One of every 300 shuttle missions to the space station could expect to be destroyed by space debris, Shannon said. By contrast, Atlantis faces a 1-in-185 risk of fatal damage, he said.