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The RADARSAT-1 satellite has become an integral tool in tracking icebergs off of the East Coast.

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The next frozen frontier
By Wayne Curtis

Just as early explorers sailing across the North Atlantic kept a watchful eye out for ice, so, it seems, do their modern counterparts.

"First thing that comes to mind is the Titanic," says Des Power of C-Core. "But a vessel going full-speed and smashing into an iceberg is different than a stationary vessel with an iceberg impacting on it."

Take those working on the space shuttle. Even though the spacecraft’s massive external fuel tank — filled with super-chilled liquid hydrogen and liquid oxygen — is coated with dense insulating foam, NASA technicians still must account for the warm, humid air at the Florida launch pad, which can condense and freeze. Rain may also freeze. Astronauts certainly don’t want slabs of ice ripping off the tank and slamming into the shuttle as they streak into space.

That’s where Bob Gagnon comes in.  A US Army research facility (Tank Automotive Research, Development and Engineering Center, or TARDEC) that assesses ice sensors on behalf of NASA, approached him in 2004 looking for a way to measure the ice forming on the tank during the countdown to improve safety at liftoff.

Gagnon’s device, is one of three that has been considered by TARDEC. It involves a relatively simple laser rigged to a telescope. Light is beamed at the surface that has a thin layer of clear ice on it. The light beam passes through the ice to create a bright spot on the surface, scattering light in all directions. Some of this scattered light passes back out through the top of the ice and some reflects back down to the underlying surface. “At a certain critical angle all the light is internally reflected back onto the surface, creating a bright ring,” says Gagnon.  “The diameter of that ring is directly proportional to the thickness of the ice.”

The device, which performed well during initial testing in Michigan last year, was operated up to 30 metres from ice-coated shuttle foam samples. Gagnon is still fine-tuning a similar technique to measure the thickness of cloudy ice — the most common type of ice formed on the shuttle external fuel tank — since it presents a whole other set of challenges.

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