Traveling along with the space station and hundreds of satellites is a swarm of more than 16,000 bits and pieces of rocket parts traveling at high velocities. Any one could pose a threat to both humans and machines in orbit. In a report released today, a worried National Research Council (NRC) committee urged NASA to take this threat more seriously with a more coordinated program to track, avoid, and even remove this dangerous debris.
Space junk is as old as the space program, but it leapt to the attention of the White House following a 2007 Chinese antisatellite test and a 2009 collision of a Russian spacecraft with a U.S. communications satellite. The intentional Chinese test alone added more than 3000 pieces of material to the cloud of space junk circling Earth.
The sudden and dramatic increase in debris caused by these two events forced NASA to swerve its massive Terra satellite to avoid being hit by a piece of Chinese junk. It also prompted fears for the safety of its astronauts on the international space station, which recently experienced a near miss. In April 2010, at the urging of the White House Office of Management and Budget and the Office of Science and Technology Policy, NASA asked the National Academies' NRC to suggest ways to cope with orbital debris.
"The current space environment is growing increasingly hazardous to spacecraft and astronauts," said Donald Kessler, who chaired the 13-person panel. Kessler is a retired astrophysicist who warned in 1978 that colliding debris would set off a chain reaction, creating more junk. His committee recommended that the space agency come up with a strategic plan that would centralize an effort now scattered across the agency, insulate the work from budget and personnel cuts, and update analytical models of how small and large particles act as they orbit Earth.
The U.S. Air Force is responsible for detecting, tracking, and identifying human-made objects in orbit, and has catalogued 16,000 objects that are larger than 1 centimeter across. The exact number fluctuates as some pieces burn up in orbital reentry and as new pieces enter orbit. Nearly all space-faring nations have contributed to the ring of junk, although the United States is responsible for one of the largest shares, approximately 30% of those objects. The former Soviet Union and China are responsible for most of the remainder.
Predicting which objects might hit an operating spacecraft requires intense modeling. NASA's Johnson Space Center in Houston set up an office in 1979 to tackle the problem. Since 1990, researchers have been using a ground-based x-band radar to track movements more exactly. But the NRC panel is worried that a host of tiny particles are not being adequately followed, and that the complexity of those movements is not yet understood fully.
Cleaning up the mess would require another order of knowledge and funding. And it might not even be legal, since "you can't take, touch, or salvage space objects from another country," says Joanne Gabrynowicz, a panel member and space law expert at the University of Mississippi in Oxford. "Even if you are only dealing with U.S. objects," she says, "you still want people to know what you are doing."
She notes that there is no prohibition against creating space debris, although the Outer Space Treaty calls on spacefaring nations to "avoid harm." As a first step, the panel recommends that the U.S. State Department consider the diplomatic aspects of removing debris, while researchers consider ways to minimize junk on orbiting rockets and possible ways to sweep orbits clean.
Legal scholars say the United States shouldn't go it alone. "International coordination is absolutely necessary," says James Dunstan, a lawyer with Mobius Legal Group in Virginia, who is familiar with the legal issues of space debris. "We have got to come to an international understanding."