26 July 2012
A tiny satellite can be seen flickering high above the Earth in the simulated video above. This could be a typical serene view you might see if you went far from city lights and looked up at the night sky.
Except this virtual satellite is a dangerous piece of space junk, careening through space on what may eventually be a collision course. Researchers are now working to extend our ability to track orbital debris and help avoid such a catastrophic outcome.
Space debris, or space junk, is made up of tens of millions of man-made objects that have been discarded, lost, or left in orbit. Some pieces are fairly large — spent rocket stages or defunct satellites — but the majority is incredibly tiny, including flecks of paint and eroded bits from other spacecraft.
The problem is that all these pieces are moving incredibly fast, sometimes more than 17,000 mph, and when they collide they can cause tremendous damage, destroying expensive satellites and creating more space junk. In 2009, an Iridium communications satellite hit the Russian Cosmos spacecraft, creating a heap of new litter.
Orbital junk also threatens human activity in space. A hole just 0.4 inches in the International Space Station’s hull could cause a catastrophic implosion, leading astronauts to go scrambling for the Soyuz escape craft when dangerous pieces fly by.
“If we don’t do something soon, low-Earth orbit will be just useless,” said engineer John Crassidis of the University at Buffalo in New York.
NASA currently tracks about 22,000 pieces of space junk in low-Earth orbit – which is about 100 to 1,000 miles above the surface where many satellites and the International Space Station fly. But the problem has also expanded farther out, to high-Earth orbit, approximately 22,000 miles above the surface, where weather monitoring and communications satellites are located.
Ground-based telescopes and orbital satellites can image low-orbit space junk larger than about 4 inches (roughly the size of a baseball), helping to determine whether those pieces might cause problems. But our capabilities can’t really make out objects in high-Earth orbit. Crassidis and his team are working on computer models that plot the brightness of debris objects as they turn and reflect glints of sunlight to help resolve their size and shape. The work could be useful in avoiding future collisions in both low- and high-Earth orbit.
New monitoring efforts are also helping tackle the problem. In the last couple of years, both the Space Based Space Surveillance System and DARPA’s ground-based Space Surveillance Telescope have improved our ability to track space junk. Eventually, the United States will be able to follow between 100,000 and 600,000 pieces of debris.
“The good news is that now we can track a lot more stuff, but the bad news is that now we have to track more stuff,” said Crassidis.
Determining the chances of any collisions between all these objects and the many satellites and spacecraft in orbit will require increased computing power, he added. Engineers will need to figure out a good solution to deal with all the data.
While monitoring efforts are a good first step, there’s still the problem of actually trying to clean up space. Researchers have proposed shooting the junk down with lasers, recycling it into new satellites, or sending a dedicated spacecraft to sweep it up.
Whatever the most viable solution turns out to be, it will be needed sooner rather than later. Last year saw the largest deployment of new spacecraft in a decade. At the same time, the amount of space junk has grown nearly 8 percent since 2010.
“We know one thing for sure: Without some sort of solution, putting a satellite in low-Earth orbit will be impossible within the next 20 years,” said Crassidis.