An artist’s impression of catalogued objects in orbit viewed over the Equator. (AP photo/European Space Agency)
Space debris – a growing concern
ASK THIS | May 06, 2009
How’s this for a collision: In February, one satellite smashed into another at a closing speed of 22,000 miles per hour. Both were destroyed, creating almost 900 pieces of trackable debris.
By Victoria Samson
2008’s “Wall-E”, an animated science fiction film, showed a planet choked by rings of orbital debris to the point where outgoing traffic had to dodge its way through en route to the stars. While we are unlikely to ever hit that level of Hollywood space pollution, there are still very real concerns about what negative effects orbital debris – junk from earlier space missions, old satellites, and other man-made objects – could pose to spacecraft and working satellites.
On March 12, 2009, the crew of the International Space Station (ISS) was forced to prepare for an emergency evacuation inside the Soyuz spacecraft in response to an unexpected close approach by a piece of debris from the 1993 U.S. launch of a Global Positioning Satellite.
This was followed by another close approach by a piece of debris from an expired Russian satellite on March 16. On March 22, the docked Space Shuttle Discovery and ISS were forced to change orbit to avoid an extremely close piece from a Chinese rocket booster launched in 1999. Earlier in the year, on February 10, a U.S. communications satellite owned by the Iridium Satellite, LLC collided with an inactive Russia military communications satellite at an altitude of 789 kilometers (490 miles) and a closing speed of 10 kilometers per second (22,000 miles per hour). This resulted in the destruction of both objects and the creation of almost 900 pieces of trackable debris.
The primary source of information on space debris is the U.S. military’s Space Surveillance Network (SSN), which is currently tracking over 19,000 man-made objects circling the planet that are greater than 10 centimeters (four 4 inches) in diameter. Of these, only about 900 are active satellites with another 2,300 being dead or inactive satellites. If sensor capabilities improved to allow tracking of even smaller objects, we would potentially be tracking another 300,000 or more pieces bigger than about half an inch. This, however, leaves the potentially billions of still smaller pieces undetected, and given the dizzying speeds at which they orbit our planet, even a paint chip-sized fragment could prove lethal to an astronaut on a space walk or a delicate satellite instrument.
Once in orbit, many objects tend to stay there for long periods of time because there are very few outside forces that would cause them to come down. For those in very low orbits, the drag from the Earth’s atmosphere will eventually cause them to decay naturally and burn up. But at higher altitudes of more than a few hundred miles, space debris has a lifespan of decades, if not centuries or millennia.
While space debris exists at all altitudes and orbits, it is largely concentrated in the areas where most of humanity’s space activity has been focused: at an altitude of 805 to 1,127 kilometers (500 to 700 miles) in an area called Sun-synchronous orbit. This region is far enough above the atmosphere that any debris in it will stay in orbit for many centuries, creating the potential for more collisions and debris-creating events in the future.
So what should reporters and editors be asking policy-makers about orbital debris?
Q. Can debris be created intentionally?
Debris can be created not only from accidents between space objects but also, more worryingly, from the intentional destruction of satellites. Both the United States and the Soviet Union conducted several anti-satellite tests during the Cold War that created space debris. More recently, China’s anti-satellite test of January 2007 – where it deliberately shot down one of its old weather satellites – created 2,400 pieces of trackable debris that are expected to be on orbit for centuries. Thus far, only 58 pieces from this event have de-orbited. The United States destroyed one of its nonfunctioning satellites in February 2008, but because it did so at a very low altitude right before the satellite re-entered the atmosphere, the trackable debris remained on orbit for a relatively short eight months.
Q: How can we ensure the long term sustainability of outer space?
The best way to ensure that billion-dollar space missions, including those involving astronauts, are not threatened by debris is to prevent the debris from being created in the first place. The United Nations (UN) Space Debris Mitigation Guidelines, which are based on the work done by the Inter-Agency Space Debris Coordination Committee (IADC), establish operating procedures that are intended to be incorporated into the activities of space-faring nations so that the amount of debris that would be created by space activities is minimized.
Additionally, we need to improve the knowledge we have about the space environment and the effects our use has on it. A system of international civil space situational awareness could allow for the sharing of information about potential threats on orbit between interested actors so that all satellite owners have sufficient warning to move their satellites in case of a pending collision or do not mistake outages due to a space weather event to a hostile act.
Finally, states can come to consensus on additional ways to avoid creating debris and minimize its impacts. At present, there is no international treaty preventing the deliberate creation of space debris. There is, however, growing support for “rules of the road,” where space-faring nations agree to certain types of behavior (a “code of conduct”) to ensure the responsible use of space simply out of sheer self-interest. While this is not as legally binding as an international treaty, it can lay the groundwork for future cooperation, and in the meantime, strive to ensure that space craft and satellites are in less danger from space debris.
Q: What is the White House’s policy regarding debris mitigation?
Nothing specific has been stated as of yet. The United States is working on a new National Space Policy (NSP) that is intended to replace that of the Bush administration, but it is not expected out until the beginning of 2010 at the earliest. The White House Web site asserts that it will “thoroughly assess possible threats to U.S. space assets and the best options, military and diplomatic, for countering them.” Space debris is one of these threats, and the United States should not limit itself to unilateral solutions to combat it. In the meantime, by continuing to implement the IADC’s debris mitigation guidelines and improving space situational awareness, the United States as one of the preeminent space powers – and the country that is most dependent on its space assets - can do its part to guarantee that “Wall-E”’s vision of a polluted space environment remains strictly a matter of fiction and thus help ensure both the security of vital U.S. space assets and the long term sustainability of outer space.