Wider-view satellites ideal surveillance measure for northern waters

Wider-view satellites ideal surveillance measure for northern waters

University of Queensland research has shown how radar "eyes in the sky" can be opened four times wider to vastly improve Australia's northern waters surveillance.

For his PhD with the Co-operative Centre for Sensor Signals and Information Processing (CSSIP), Dr Glen Callaghan developed a new technique enabling a radar imaging satellite to "see" a 400km-wide strip or "swath" - four times wider than current satellite technology allows.

A satellite built to Dr Callaghans' design and launched into an orbit near the equator would be well-positioned to cover Australia's northern waters, he said.

"The frequent passes of the satellite in this near-equatorial orbit together with the extra-wide swath would allow the same area to be visited every few hours, detecting ships and their wakes (indicating direction) more precisely," he said.

He estimated it would require just five satellite passes to cover Australia's northern waters.

Such a system would be especially useful for spotting illegal activities such as uncontrolled migration into Australia, piracy, fish-poaching and arms or drug-running as well as any troop movements, he said.

The PhD, supervised by CSSIP researcher Professor Dennis Longstaff applies to synthetic aperture radar satellites - a type of satellite that uses radar to produce images of the Earth's surface.

"The advantage of these relatively new spaceborne radar systems is that they can ?see' through clouds and at night. They are also highly suited to the frequently clouded equatorial region covering northern Australia," Professor Longstaff said.

"Current synthetic aperture satellites see a relatively narrow strip of about 100kms and provide complete global cover in 30 days. For this reason, they are not appropriate for regional surveillance."

Only about three radar imaging satellites circle the Earth at present. Professor Longstaff said all were in polar orbits because they had been launched by nations with higher-latitude interests.

"Our main interest is in the tropical waters north of Australia where there are no radar imaging satellites at present," Professor Longstaff said.

Dr Callaghan's design with the working name ?EquaSAR' makes satellite swaths wider without sacrificing the resolution of the pictures sent back to ground stations.

Professor Longstaff said the estimated several hundred million dollars it would cost the Australian Government was a relatively small price to pay for continued long-term surveillance of illegal activities.

"If we were able to share the system with neighbouring nations, the costs to Australia would be reduced," he said.

"This type of satellite would be very beneficial to peace and security in our region. Australia is ideally placed to be lead with such an initiative. We need to start thinking big and long term."

Dr Callaghan's PhD thesis provides a mathematical analysis of the technique and performance figures based on computer modelling.

He said he achieved the wider swath by splitting the single radar antenna on existing satellites into four sections and separately processing the data from each.

Hundreds of satellites circle the Earth each day at different altitudes. These include the common, communications satellites receiving and re-transmitting signals, remote sensing satellites monitoring environmental changes and weather patterns and navigational satellites accessed by Global Positioning Systems (GPS).

For more information, contact Professor Longstaff or Dr Callaghan (telephone 07 3365 3871 at work or 02 9519 9971 after hours or mobile 041 202 7378 or 0417 627 182).