* What goes up doesn't necessarily come down when it comes to manmade objects orbiting the planet.
During the last 52 years, the space-faring nations of the world have trashed the low, medium and geosynchronous orbits where their satellites operate. The Air Force is improving its ability to monitor all the active and dead satellites, spent rocket boosters, collision wreckage and debris from anti-satellite tests that threaten commercial, scientific and military satellites alike.
A new satellite dedicated to monitoring space is expected to be launched this year, and the service says it is improving its ability to predict possible accidents.
Until recently, though, little thought was given to ideas that would remove the trash itself.
But that has changed. The Defense Advanced Research Projects Agency and NASA are teaming up to find out what, if anything, can be done to clean up space.
It will be a daunting challenge, both technically and financially, experts said at the Space Symposium in Colorado Springs, Colo.
"The number of manmade objects continues to accumulate in orbit," said Nicolas Johnson, NASA's chief scientist for orbital debris. Of the 20,000 or so objects tracked by the Air Force, about 95 percent of them are about the size of a marble, or larger. Even something as small as one centimeter in diameter can cause a catastrophic accident, he noted. As for the unknown number of objects smaller than that size, estimates are as high as 500,000, he said.
The amount of debris could rise exponentially, Johnson and other experts have suggested. A collision creates more debris, which increases the chance for other collisions, and so on.
A case in point is the January 2009 incident where a defunct Russian Cosmos satellite slammed into an active Iridium communications satellite at a speed of about 15,000 miles perhour about 490 miles above Siberia. The accident created hundreds of objects large enough to damage other spacecraft. Johnson estimated that in the future, collisions will be the number one source of new orbital debris.
Retired Lt. Gen. Brian Arnold, vice president for space strategy at Raytheon space and airborne systems and former commander of the Air Force's space and missile systems center, said, "Virtually every time we launch a vehicle into space, we contribute and continue to contribute to space debris. Fuel tanks, bolts, and screws come loose, paint chips come off and eventually satellites die in orbit."
Johnson said, "The most effective means of curtailing the long-term hazard to operational space craft is to remove the large ... nonfunctional spacecraft and rocket bodies which now number about 4,000."
The Air Force is improving its ability to monitor objects in space and predict possible "conjunctions," which is its euphemism for collisions.
Since last year, it has catalogued an additional 500 objects, pushing the number it tracks to about 20,000.
Its series of earth-based Cold War era radars and optical sensors can track items about the size of a basketball or larger. However, many of these radars were first used to track incoming missiles from the former Soviet Union and are configured for the Northern Hemisphere. There is a lack of assets in the south, Air Force officials have said. …