Compared to the vastness of outer space, the band of space that makes up Earth orbit is tiny and becoming increasingly crowded with manmade objects.
More than 3,000 satellites and thousands of other manmade objects left behind by civilian and military space programs litter both geostationary orbit, about 22,000 miles up, and low-Earth orbit — located roughly between 60 and 200 miles above the Earth. The less-crowded medium orbit lies between the two.
Orbiting space debris includes, among other things, old satellites and abandoned rocket stages — sometimes with residual fuel that could explode, sending shrapnel into functioning satellites. Debris plays a major role in the debate over space weapons, because using a space weapon could create huge amounts of debris, and an accidental collision of debris could be misperceived as an attack.
“There are hundreds of thousands of potentially lethal objects in orbit, and millions of smaller objects that pose at least some risk,” Bruce W. MacDonald, a former National Security Council staffer, told Congress in March 2009. The problem had been “dramatically illustrated” a month earlier, he said, when a U.S. Iridium satellite collided with an abandoned Russian Cosmos rocket body, the first time two manmade space objects of such large size ran into each other.
Since then, attitudes on space debris have changed drastically, says Brian Weeden of the Secure World Foundation, which advocates the peaceful use of outer space. Before the collision, the Joint Space Operations Center (JSpOC) screened 100–150 essential, high-priority mostly American-owned objects daily — including the space shuttle, International Space Station and national security satellites — for potential collisions, he says. Now, the command screens every active satellite — about 1,000 — every day and warns satellite operators, including the Russian and Chinese governments.
Over the past year, “JSpOC has provided Russia with 252 notifications and China with 147 notifications regarding close approaches between satellites,” Frank Rose, a deputy assistant secretary of State, told the European Space Policy Institute recently in June.
The biggest single debris-creating incident in history occurred in 2007, when China shot down one of its weather satellites to test its anti-satellite capabilities. The incident expanded by 10 percent the total number of trackable orbiting objects (those larger than about four inches in diameter). It will take a century for the effects to dissipate, scientists say. (Objects in low-Earth orbit travel through a very thin atmosphere in which satellites eventually burn up.)
The Chinese test and the 2009 collision demonstrate the biggest worry regarding space debris: the risk of a chain reaction, in which colliding spacecraft generate massive amounts of space junk that in turn strikes other objects.
An artist's rendering shows the thousands of pieces of manmade debris that circulate in low-Earth orbit. Debris created by the use of a space weapon could create huge additional amounts of space junk that could accidentally destroy satellites and possibly be misperceived as an attack. (AP Photo/ESA)
Two NASA scientists predicted such collisions in the late 1970s. “According to their models, large pieces of space debris would get hit by smaller pieces of debris, creating hundreds or thousands of new pieces of small debris, which could then collide with other large pieces,” Weeden said in a paper this year. The process, which they called “collisional cascading,” would cause the amount of space debris to increase “at an exponential rate and significantly increase the risks and costs of operating in space.”
To prevent such chain reactions, engineers have suggested modifying the orbits of large pieces of debris — such as old rocket bodies and defunct satellites — so they either burn up in the atmosphere or are moved to less-congested orbits. Darren McKnight — a former Air Force officer who works for the defense contractor Integrity Applications — says developing and utilizing debris-removal technology, such as lasers or space tugs, should begin immediately. “Pay me now, or pay me more later,” he told a 2010 conference.
But so far no such technology exists. And Andrew Palowitch, director of the Pentagon's Space Protection Program, says some countries might consider such technology a weapon.
Nancy Gallagher, assistant director of the Center for International and Security Studies at the University of Maryland, says it's “infinitely more sensible to stop creating debris in the first place.” Only 11 of 21 spacecraft in geostationary orbit that stopped functioning in 2009, she says, were disposed of properly — meaning they were either sent into the lower atmosphere to burn up or put into out-of-the-way “parking orbits.”
— Konstantin Kakaes