The space around Earth is becoming more cluttered by the day with orbital junk that, if left unchecked, will pose an ever-increasing threat to current and future spacecraft, a panel of experts told a Congressional subcommittee on Tuesday.
While space debris levels rose this year after the Feb. 10 collision between U.S. and Russian satellites, more rigorous tracking and cleaner spacecraft could help avoid such orbital smashups in the future, the panelists said.
?The threat posed by orbital debris to the reliable operation of space systems will continue to grow unless the sources of space debris are brought under control,? NASA?s chief orbital debris scientist Nicholas Johnson told the House Space and Aeronautics Subcommittee in Washington, D.C.
More junk in space
The Department of Defense?s Space Surveillance Network, which relies on a global network of monitoring stations, is currently tracking more than 19,000 objects in Earth orbit larger than four inches (10 cm), but there are an estimated 300,000 total objects bigger than a half-inch (1 cm) in size circling Earth. In 1980, the network was tracking just 4,700 objects, about 2,600 of which were space trash.
?So in 29 years, the amount of space traffic has quadrupled,? said U.S. Air Force Lt. Gen. Larry James, commander of the U.S. Strategic Command?s Joint Functional Component Command for Space.
February?s satellite crash was the largest debris event since China intentionally destroyed a weather satellite in a 2007 anti-satellite test. But most of the man-made junk in space stems from fragmentation events, in which old and malfunctioning spacecraft break apart or explode.
?It is clear to me that if the spacefaring nations of the world don?t take steps to minimize the growth of space junk, we will eventually face a situation where low Earth orbit becomes a risky place to carry out civil and commercial space activities,? said Congresswoman Gabrielle Giffords (D-Arizona), the committee?s chair.
The fastest way to reduce the risk to satellites and manned spacecraft from space debris is to enhance a pilot program by the Department of Defense to alert commercial U.S. and foreign satellite operators of potential collisions so they can be avoided, Johnson said. That pilot project - the Commercial and Foreign Entities program - is expected to become operational later this year, James added.
There are also efforts to upgrade the Space Surveillance Network, James said. The network cannot continuously track every one of the nearly 800 satellites currently in orbit that have the capability to dodge potential collision. Efforts are under way to set up that capability by sometime next year, he added.
If funding comes through for a planned Space Fence, which would use new sensors to fill in network gaps, it could boost the number of objects tracked in space from 19,000 to nearly 100,000, James said. The Pentagon plans to launch a new satellite later this year to test space-based debris monitoring assets, he added.
Richard DalBello, vice president of government relations for the satellite communications firm Intelsat, also said that attaching government space debris sensors on commercial satellites is another possible countermeasure.
Space trash pick up
Adhering to relatively simple practices, like venting a satellite?s fuel supply at mission?s end to avoid explosions and adding devices to catch severed bolts instead of blowing them out into space, can be effective in limiting the growth of unnecessary space trash, said Scott Pace, director of the Space Policy Institute at George Washington University. But other potential orbital mop up methods - such as firing Earth-based lasers at trash in space, carry political issues beyond their technical hurdles.
?There?s a fine line between a ground-based laser for cleaning orbital debris and a weapons system,? Pace said. ?So you?d have to have an amount of international discussion to decide whether that makes any sense.?
Congressman Dana Rohrabacher (R-California) said that a while monitoring the space debris environment is vital, a more effective means of cleaning up the orbital junk already in space is also needed.
?If you?re already charting the course, all we have to do is get something up there that will knock it down,? Rohrabacher said. ?And that doesn?t have to be something so sophisticated. Just a big bulldozer in the sky, you might say.?
The satellite collision above Siberia increased the risk of damage from space junk to spacecraft across a wide range of Earth orbits that include the Hubble Space Telescope, Earth observation satellites and astronauts aboard the International Space Station. It increased the risk to NASA?s station-bound space shuttles by about 6 percent, or a 1-in-318 chance of damage, the space agency said.
NASA plans to launch the shuttle Atlantis to the Hubble Space Telescope on May 11, though the agency has said the increased space debris environment at the iconic observatory 372 miles (600 km) above Earth is one of the mission?s top risks.
After a detailed analysis, the space agency found the risk of catastrophic damage from space debris around Hubble to be about a 1-in-221 chance, within acceptable limits. NASA?s guidelines call for no greater than a 1-in-200 chance of serious space debris damage.
The space agency plans to position Atlantis in an orientation that provides extra protection for astronauts working outside the shuttle during the Hubble repair mission?s five spacewalks. The shuttle will also fly into a safer orbit soon after completing its work at the space telescope, NASA officials said.
A second space shuttle, Endeavour, is also on a separate launch pad and poised to serve as a rescue ship if needed, should Atlantis be critically damaged by space debris.
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