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See Inside November 2011

On the Trail of Space Trash

The U.S. Air Force has a new plan to track tiny pieces of orbiting debris



Courtesy of NASA Orbital Debris Program Office

Since the space age began, the orbital realm has become increasingly littered with the detritus of skyward human striving—spent rocket boosters, dead satellites, stray pieces of hardware. Debris is piling up with such speed that it has become a threat to the kind of spacefaring endeavors that spawned it in the first place.

A September report by the National Research Council found that the debris field is so dense that collisions between objects in orbit will create additional debris faster than space junk falls out of orbit. The predicted outcome: an exponential growth of the number of pieces of space debris.

Already millions of pieces of refuse five millimeters and up circle Earth in a high-velocity swarm, each packing enough kinetic energy to disable a satellite. Far more sobering is the threat to human life. In June the six astronauts onboard the International Space Station took shelter in escape capsules when a piece of debris came within a few hundred meters of the station.

The U.S. is now taking preliminary steps to manage the threat of space junk by implementing better tracking systems. Space Fence, a new $6-billion radar system that the U.S. Air Force is planning, could dramatically increase the number of orbital objects under surveillance after it comes online around 2017.

As planned, Space Fence would comprise two radar stations in the Southern Hemisphere, which will take over for a 1960s-era radar system. Whereas the present system operates in the VHF band, Space Fence will use shorter-wavelength S-band radar, which affords better resolution for tracking debris. “The smaller the wavelength, the smaller the objects,” says Scott Spence, director of Raytheon’s Space Fence program. Raytheon and Lockheed Martin are vying for the government contract. The current debris catalogue goes down to roughly softball-size objects, but Space Fence, Spence says, may be able to track objects as small as a marble at lower altitudes.

Space Fence and other smaller-scale projects aim to increase what the military calls “space situational awareness.” How that awareness might progress to remedial action—the removal of orbital debris—remains unclear, though. 

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