When the Chinese government destroyed one of its weather satellites in a military test last month, it sent a chill through the U.S. military.
And engineers say it had a serious side effect -- it increased the amount of orbiting space junk by about 10 percent.
That could mean danger -- to other satellites, and even, possibly, to astronauts on the International Space Station and future space shuttle flights.
"There's a lot of stuff up there in low-Earth orbit," said T.S. Kelso, a veteran space-surveillance analyst who is now at the Center for Space Standards and Innovation in Colorado Springs, Colo. "While we can't tell them that 'five months from now, you're at risk for being hit,' it's not unreasonable to expect that it's going to affect a lot of stuff in orbit."
500 Pieces of Debris, Possibly Thousands More
The Chinese test, carried out on Jan. 11, was at once complex and very simple. An old weather satellite, passing 537 miles overhead, was targeted by a missile launched from a Chinese military base.
The missile hit the satellite with deadly precision. The missile carried no bomb because it didn't need one. The satellite was pulverized by the impact.
But what followed was chaos in space. As of today, Kelso reports that American radar is tracking at least 525 pieces of debris from the collision -- each at least the size of a baseball.
There are probably hundreds, if not thousands, of smaller ones.
The pieces are gradually spreading out in a ring around the Earth, creating a vast area where spacecraft face increased danger of being hit.
"We've already seen in the range of 500 to 600 events where some piece of debris from this one event was coming within 5 kilometers [about 3 miles] of some payload," said Kelso.
It's a growing problem. The U.S. Air Force was already tracking almost 14,000 objects in orbit.
Three times in the last 15 years, U.S. satellites have reportedly been disabled or damaged by collisions with space junk. NASA is worried enough about the problem that each shuttle crew now spends the entire day before landing taking pictures of its ship's heat shield tiles, just in case there's been a small but potentially fatal impact.
If a shuttle crew ever does find damage, the astronauts would have to seek safe haven on the International Space Station, and wait for a second shuttle to get them. Such an accident, NASA's administator, Michael Griffin, has said, would probably mean the end of the shuttle program.
The Chinese weather satellite, designated Fen Yung-IC, was in an orbit that took it over the North and South poles. It's an orbit that's popular for weather, reconnaissance and Earth-science satellites because it allows daily pictures of virtually every part of the planet below.
"There are about 125 or 130 satellites in that same orbit," said Theresa Hitchens, head of the Center for Defense Information, a Washington-based group that provides information on national defense and aerospace isues. "It's a highly used orbit, and it's an orbit that's already fairly polluted."
Shuttles travel in a very different path; all but one of the remaining 13 missions is scheduled for assembly of the space station, about 220 miles high. But the ring of debris from the Chinese debris has already spread out enough that the station passes through it twice on every 90-minute orbit of the earth.
How great is the danger? They don't call it "space" for nothing; there is a lot of empty void in the realm where most spacecraft orbit. NASA has said it's not worried.
But the debris from the Chinese test has added to the small chance of a big catastrophe.
"We can't see it, we can't track it," said Hitchens, "and something as small as a marble can shatter a satellite."