[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2009/TECH/science/03/30/space.rocket.sound.light/art.space.sound.light.debris.gi.jpg caption="A mysterious flash in the sky Sunday night may have been debris from the Soyuz spacecraft's booster."]
Caroline S. Reilly and Peter D. Zimmerman
The fireball that streaked across the southeast U.S. skies Sunday night may have been the remnants of a Russian rocket booster.
A week earlier, the crew of the International Space Station briefly took shelter in their escape capsule because of worries about a piece of space junk no more than six inches across.
A month before that, a pair of camper-sized communications satellites slammed into one another above northern Siberia, causing thousands of metal shards ranging in size from dust speck to cantaloupe to be shot into space at speeds of over 17,000 mph.
Celestial real estate is increasingly popular. Now that Iran has joined the space club, 10 countries have demonstrated the ability to launch a probe into orbit, and another 100 own or share a satellite launched by others. All in all more than 900 satellites, along with tens of thousands of bits of man-made space detritus, jockey for elbow room overhead.
The result: a growing threat our atmosphere will soon become so crowded with floating junk as to become almost unusable.
Even the tiniest of the shards from the Siberian collision is capable of disabling or destroying any other satellite it might hit. As greater numbers of commercial, military and government enterprises require space-based components, more such instances, and potentially collisions, are likely.
Orbital debris is the gravest threat to new and existing space systems. The U.S. government’s list of detectable objects in space grew to more than 10,000 after China demonstrated its anti-satellite technology in 2007. However, that list only includes objects larger than two to four inches in size. The thousands of smaller fragments are also dangerous.
The sheer numbers – and lack of a mechanism to clean up space debris – enhance the odds that more orbital junk may render portions of space temporarily or permanently unusable if left unchecked. NASA experts Donald Kessler and Burton G. Cour-Palais wrote decades ago that without the means to remove space debris, the level of litter in more densely populated orbits would reach a critical point.
At that point, a collision between two objects of sizable mass could start a space “domino effect”: each shrapnel cloud would collide with more satellites, creating subsequent impacts, and more debris, until space becomes a nearly impenetrable cloud of junk.
Satellites in a region of space known as the geostationary belt are particularly vulnerable. These spacecraft are situated in a tiny volume of space where they circle Earth once every 24 hours, to the second. This causes them to appear “fixed” above a given spot on Earth’s surface. A 24-hour orbit makes possible communications satellites, direct broadcast television, and satellite radio networks. The geostationary orbit is so high – 22,000 miles – that there is no air drag, and the fragments from a space wreck would remain there for many millennia.
If a cascade of collisions started in the geostationary belt, it is possible the entire belt would be closed for business, permanently. An incident like last month’s could render the most valuable parts of this region of space unusable.
The international community can take debris mitigation measures to avoid such calamity. The first would be to reconsider the development or deployment of anti-satellite technology designed to destroy orbiting spacecraft. This month’s collision illustrates the threat debris clouds pose to satellites. Technology that enables the intentional creation of debris clouds would put the satellites of all nations at risk.
A second step would be to pay attention to prudent spacecraft design that curtails the creation of harmful space junk. Spacecraft can be designed to expel less debris. Power and cooling components must be improved to reduce the risk of explosions. At the end of their lives, satellites should be deorbited into the atmosphere with one last burn from their motors.
Lastly, a set of guidelines outlining responsible outer-space activities should be universally endorsed. Such a code would be similar to those already used to reduce threatening behavior in sea and air operations. The European Union has already drafted a set of recommended practices, and the United Nations Office of Outer Space Affairs has developed a set of voluntary guidelines that focus on halting the production of debris, which a number of member countries have adopted.
The United States is one of the few nations that have opposed binding agreements to limit debris. The Obama Administration has a chance to change that policy. Otherwise, if the international space-faring community does not preserve the global commons of space, a major collision between two satellites could make whole orbits of earth, including the valuable real estate in the 24-hour orbit where communications satellites operate, unusable – possibly forever.
Editor's note: Caroline S. Reilly is a research assistant at the RAND Corporation specializing in defense strategy and planning. Peter D. Zimmerman is former chief scientist of the Senate Foreign Relations Committee and former State Department science advisor.
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