Defence Minister Robert Hill told a defence industry conference here Australia remains the world leader in over-the-horizon radar technology and US officials had specifically mentioned this capability during recent discussions on the US missile defence system in which Australia has agreed to participate.

The prime objective of the JORN system is to detect and track ships and aircraft up to 2,000 kilometres (1,250 miles) from Australia's north and northwestern coastline.

But trials conducted in 1997 in the northwest of Western Australia showed it could also detect the launch of SCUD-type missiles, Hill added.

He said the enhancements would give JORN greater range and greater ability to detect smaller ships and aircraft.

"This project at a cost of approximately 62 million dollars over a number of years will further improve the sensitivity of the operational radars and support further research on the capability to address ballistic missile threats," he said.

"Basically its principal objective was to see aircraft over large distances. Further upgrades will allow it to see much smaller objects such as missiles."

Over-the-horizon radar works by bouncing radar signals off the ionosphere, overcoming the limitations of regular radar which works on line of sight.

JORN was launched in the 1980s to develop radar coverage of Australia's north and west. But it ran into major software problems and was only declared operational in April last year.

It comprises operational radars at Laverton in Western Australia and at Longreach in the east coast state of Queensland, plus an experimental facility at Alice Springs in the Northern Territory.

Hill told reporters a memorandum of understanding on Australian involvement in missile defence was now being negotiated with the United States and would be finalised by mid-year.

He described the US interest in JORN as a vote of confidence in the system and a recognition that it could do much more than was its original intention.

"With new technologies, new science, we now have the capability for it to do more," he said.

"Better integrating the three radars will provide an even greater coverage than we have at the moment. Further improving the sensitivity of the sensor will better enable us to see objects in difficult environmental circumstances."

A small group of noisy anti-war demonstrators disrupted Hill's address, showering delegates with leaflets before they were escorted from the building by security officers.

WAR.WIRE