Space Debris Shield: Radar Station Network

(Image: European Space Agency / Rex Features)

Keeping an eye on the increasing amount of space debris is no easy task

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.