China's clutter is not lost in space

January 20, 2007|By Dennis O'Brien | Dennis O'Brien,Sun Reporter

In blowing up one of its orbiting satellites, China created a vast debris cloud that heightens concerns about the growing threat space junk poses to spacecraft and the expanding networks of weather and communication satellites.

The blast, which occurred Jan. 11 and was confirmed by U.S. officials Thursday, spread material across 2,000 miles of space, said Harvard astronomer Jonathan McDowell. The Union of Concerned Scientists estimated that there are nearly 800 debris fragments 10 centimeters or larger and perhaps 2 million smaller pieces that can also cause damage because they travel at high speeds.

Much of it will remain for decades, experts say, adding to the inventory of spent rockets, working and dead satellites and other used equipment and materials orbiting Earth.

"It used to be with space flight people worried about meteor showers. Now the much bigger danger is from man-made debris," said McDowell.

The Department of Defense's U.S. Space Surveillance Network uses 30 telescopes and radar units to track satellites and debris.

Before the Chinese rocket destroyed the satellite, the network was monitoring 14,000 pieces of orbiting hardware put into space since the Soviet launch of Sputnik I in 1957. Each year, about 200 new pieces of debris are added to the inventory. To qualify for monitoring, a fragment must at least be 10 centimeters in size - roughly the size of softball.

"Everybody's job today is a little harder than it was maybe two weeks ago," said Nicholas L. Johnson, chief scientist and program manager for NASA's orbital debris program.

Johnson said the effect of the Chinese blast will not be known for at least another week when more complete data become available from the space surveillance network, based in Colorado Springs, Colo.

But scientists say they know the impact will be severe. "This debris cloud is all over the place," said McDowell.

The Union of Concerned Scientists used NASA formulas for calculating the effects of a blast. In addition to the largest and smallest fragments, there could be 40,000 from 1 to 10 centimeters, it said. A centimeter is about the width of a fingernail.

"Anytime you start adding things up there, it's just compounding the problem," said David C. Wright, a physicist with the scientists group.

Yesterday, the group called on the United States to enter international discussions focused on banning the testing and use of anti-satellite weapons.

Experts say the remains of the Chinese satellite and missile pose little risk of falling to Earth. Debris that reaches the atmosphere will be so small it should burn up.

But the Chinese satellite was in an area heavily used by military and commercial satellites, and because it was more than 500 miles up, much of the debris will remain in space for at least a decade, Wright said.

"This was a particularly bad place in space to do this," he said.

The Chinese test was the first of its kind since the U.S. and the former Soviet Union destroyed satellites with missiles in the mid-1980s. But those satellites were at lower altitudes, so debris from them reached the atmosphere faster and was destroyed, Wright said.

He and other experts said the Chinese test also shows the vulnerability of spacecraft and the satellites that form the basis of many cell phone, global positioning and other communications networks.

Since the Challenger explosion in 1986, NASA's space shuttles have had to reroute their paths to avoid space debris half a dozen times, Johnson said. An average of two windows have to be replaced after each shuttle mission because of debris damage.

The International Space Station has had to maneuver several times to avoid damage.

The European Space Agency estimates there could be as many as 50,000 uncatalogued objects larger than a centimeter that could pose a threat. Even small fragments - traveling about 18,000 miles an hour - can do tremendous damage because of their speed.

In 2005, a 31-year-old rocket engine collided 550 miles over Africa with a fragment of a Chinese rocket that had blown up five years before. Five years ago, the European Space Agency found thousands of impact marks on solar panels that were in space for eight years providing power to the Hubble Space Telescope.

In recent years, NASA and the European Space Agency have taken steps to cut back on space debris, minimizing the amount of disposable supplies used by astronauts and equipping rockets with sufficient fuel to re-enter Earth's atmosphere where they can quickly burn up, experts say.

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