Canadian scientists are returning to a remote Arctic island where Cold Warriors once eavesdropped on Russian submarines to test a new generation of high-tech detectors intended to watch over the increasingly busy northern waters Canada claims as its own.

If any ships try to sneak through the Northwest Passage this August, CANDISS will be watching. "This is the first baby step," said Luc Forand of Defence Research and Development Canada at Valcartier, Que.

Forand is among a team of researchers heading to Gascoyne Point on Devon Island to set up and test the Canadian Arctic Night and Day Imaging Surveillance System. The idea, he said, is to use this relatively narrow, 75-kilometre-wide stretch of water off the point to help monitor traffic through the passage.

"This is sort of like a choke point," Forand said.

Arctic observers have long warned that melting sea ice will open greater stretches of once-frozen ocean to navigation. They say if Canada claims to control waters such as the Northwest Passage, it must first be able to monitor who's in them.

Ships passing through the North are not obliged to register with the Canadian Coast Guard, although most do. In recent years, several private boats have entered the passage and landed illegally on Canadian shores.

"[The tests] are trying to provide 24/7 above-air or land-or-sea and undersea capability, something that we've never had," said Rob Huebert of the Centre for Strategic Studies at the University of Calgary.

CANDISS combines a laser, a thermal imager and two telescopic devices with wide-angle and telephoto capability. It is intended to work day or night, fair weather or foul, to pick up any traffic on the Barrow Strait. It will be combined with various radar systems as well as underwater microphones.

There's a reason the team is headed back to Gascoyne Point.

"This site has been used in the past," said Forand. "It was used for underwater research. There was an acoustic system put in there."

That old "acoustic system," which will be used for this summer's tests, could be the remains of Cold War-era spy microphones, said Michael Byers, an international law professor at the University of British Columbia.

"One of the worst-kept secrets in Ottawa is that the U.S. put underwater listening devices in the Northwest Passage with Canadian assistance," he said.

Forand's 20-member team will be conducting tests from Aug. 4-21. During that time, traffic through the strait is expected to be about one ship a day — mostly cargo and cruise ships.

"At the end of the year we hope to have a good demonstration of what the technology is capable of doing," Forand said.

Still, problems in the difficult Arctic environment are expected, and more tests are scheduled through 2010.

If the tests are successful, CANDISS will be used in conjunction with other tools, such as space images from Radarsat-II, overflights by Aurora surveillance planes and human patrols. The idea will be to combine wide overviews of the Arctic with precise and detailed information from strategic points.

The CANDISS tests have a budget of about $1 million, part of a $10-million program called Northern Watch.