The Hubble Space Telescope, once the joke of late-night comedians, has proved to be an invaluable resource in photographing the universe. NASA undertook a very expensive mission to send up the space shuttle Atlantis in an attempt to extend the telescope's lifespan so that it can continue to serve its purpose.
So imagine how much of a loss it would be if a piece of space debris rammed into it, ending its mission prematurely. It and all the other spacecraft must keep a wary eye out for the hundreds of thousands of pieces of manmade debris that circle our planet.
On May 13, a four-inch piece of space trash passed within 1.7 miles of the Hubble. At its current altitude of 350 miles, this means the two objects were moving at such dizzying speeds that an impact could be catastrophic.
This orbital debris was not like many other pieces, a cast-off part from an earlier space mission. Instead, it was created in January 2007 when China tested an anti-satellite (ASAT) weapon, using one of their ballistic missiles to shoot down an aging Chinese weather satellite. This event, according to Joseph Rouge, head of U.S. National Security Space Office, created debris that "will be around 3,000-4,000 years."
China certainly was not the first country to test ASAT weapons - the United States and the Soviet Union both held tests during the Cold War - and debris from the last official U.S. ASAT test in 1985 took 19 years to de-orbit and is no longer a threat to satellites. Debris from the Soviet tests is still up there.
The U.S. Space Surveillance Network (SSN) is currently tracking over 19,000 objects. Of these, fewer than 900 are active satellites and another 2,300 are inactive satellites. But this is just the tip of the iceberg: given sensor improvements, the United States could track at least 300,000 more objects that are half an inch and bigger, yet still not be able to monitor everything surrounding our planet. U.S. officials worry that a non-tracked piece of debris may unexpectedly crash into a spacecraft or satellite, wrecking it permanently. What you don't know apparently can hurt you.
The piece of debris from the Chinese ASAT test that passed so close to the Hubble was tracked and U.S. officials decided that in this particular case, the telescope did not need to be moved. However, in 2008, on five separate occasions other spacecraft had to shift in their orbits in order to avoid colliding with some debris. This requires using up some of the precious fuel that the spacecraft take on their missions, and in many cases interrupting the services and data the satellites provide.
Of course, given the alternative, a shortened lifespan is better than complete annihilation. In February 2009, a U.S. Iridium satellite collided with an inactive Russian communication satellite, creating almost 900 bits of trackable debris (and an unknown number too small to track but still dangerous).
What can be done about this? Ideally, the debris wouldn't be created at all. The United Nations has endorsed a set of voluntary debris mitigation guidelines presented by a worldwide group of civil space agencies, including NASA. The United States and several other nations are implementing these measures. However, more than 40 different countries currently own or operate satellites so implementation needs to be more widespread. Meanwhile, the United States is working on improving its space situational awareness so that it can continue to monitor and track debris.
Finally, abstaining from using destructive ASAT weapons ensures that damaging debris isn't created that will be around for eons. With over 400 satellites on orbit, the United States stands to lose the most if space becomes a shooting gallery.
Victoria Samson is the Washington Office Director for the Secure World Foundation, an organization that focuses on the secure and sustainable use of space.