A WORLDWIDE network of radar stations could tackle the ever-growing problem of space debris – the remains of old rockets and satellites that pose an increasing threat to spacecraft.
The US government is launching a competition, which will run until the end of 2010, to find the best way of tracking pieces of junk down to the size of a pool ball. Three aerospace companies – Northrop Grumman, Lockheed-Martin and Raytheon – have each been awarded $30 million by US Air Force Space Command to design a “space fence” that will constantly report the motion of all objects 5 centimetres wide and larger in medium and low-Earth orbits.
“It’s basically going to be an electronic tripwire,” says Rich Davis, Northrop’s special projects director in Linthicum, Maryland. “It will give you the orbit angle and time of day that every satellite or piece of debris passes any point you choose.” Once you know that, he says, it is easy to calculate potential collision risks.
It will give the orbit angle and time of day that every piece of debris passes any point in space you choose
The fence will be a significant improvement on the US’s current system – the Air Force Space Surveillance System – which was built in 1961. This covers space above the continental US and can only resolve and track objects that are at least 50 centimetres across, using VHF signals in the megahertz range. To track smaller objects requires S-band radar, in the gigahertz range.
The contenders will have to work out how best to construct a global network of S-band radars that will allow them to continually feed data to the Joint Space Operations Center at Vandenberg Air Force Base in California. JSpOC will in turn make data that is not militarily sensitive publicly available on www.space-track.org.
There are now some 16,000 pieces of debris larger than 10 centimetres wide in orbit – and recent events highlight the need for an effective monitoring system. On 13 February, a communications satellite called Iridium 33, used chiefly by the US Department of Defense, smashed into a defunct Soviet-era satellite, Cosmos 2251. By June, the collision’s leftovers had fragmented into at least 1500 pieces of debris larger than 10 centimetres, according to Nicholas Johnson of NASA. And in 2007, China created about 2700 pieces of debris when it blew up a redundant weather satellite using a ballistic missile.