A WORLDWIDE network of radar stations could tackle the ever-growing problem of space debris 鈥� 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 鈥� Northrop Grumman, Lockheed-Martin and Raytheon 鈥� have each been awarded $30 million by US Air Force Space Command to design a 鈥渟pace fence鈥� that will constantly report the motion of all objects 5 centimetres wide and larger in medium and low-Earth orbits.
鈥淚t鈥檚 basically going to be an electronic tripwire,鈥� says Rich Davis, Northrop鈥檚 special projects director in Linthicum, Maryland. 鈥淚t will give you the orbit angle and time of day that every satellite or piece of debris passes any point you choose.鈥� Once you know that, he says, it is easy to calculate potential collision risks.
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鈥淚t will give the orbit angle and time of day that every piece of debris passes any point in space you choose鈥�
The fence will be a significant improvement on the US鈥檚 current system 鈥� the Air Force Space Surveillance System 鈥� 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 .
There are now some 16,000 pieces of debris larger than 10 centimetres wide in orbit 鈥� 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鈥檚 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.
The new space fence is keenly anticipated by Richard Crowther of the British National Space Centre. It will be 鈥渁n upgrade that will greatly enhance the ability to observe and respond to the threat of space debris鈥�, Crowther says.
