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Lasers to nudge space junk out harm's way
Scientists believe light from ground based lasers could reduce the dangers of space junk.

There are more than 19,000 objects larger than ten centimetres orbiting the Earth, and studies warn the problem's getting worse.

Now a report on the pre-press website by a team of researchers at NASA's Ames Research Center, claims commercially available lasers and technology used on telescopes, could move space junk out of harms way.

The team were looking at the effect of light radiation pressure from the Sun on satellite orbits and wondered if a laser slightly more powerful than sunlight could change debris orbits.

"The physics is the same as using the light pressure of photons to propel solar sails through space, and would be a fraction of the cost of physically collecting disused equipment and debris in orbit," says James Mason, a contract scientist with the University Space Research Association.

"Simulations show a 5 kilowatt laser used for industrial wielding and cutting, combined with adaptive optics used on telescopes like Mount Stromlo's [Satellite Laser Ranging facility], would over a few days provide enough momentum to move objects sufficiently to avoid a significant proportion of predicted collisions."
Laser weapons

According to Mason previous laser concepts used high-powered beams to ablate the target, providing enough energy to force it to de-orbit and burn up in the atmosphere.

"One of the problems with lasers of that power is that they can be perceived as military weapons. We wanted something far less threatening," he says.

"We aren't trying to deorbit objects, just prevent collisions. To actually deorbit a target would require a thousand times more power than we're talking about."

"Our vision is an international collaboration having the system going continuously, engaging multiple debris targets one after another. By doing this for enough objects the population of space junk will eventually decline."
Kessler syndrome

In 1978, NASA scientist Donald Kessler predicted a collision between two pieces of space junk could trigger a cascade of further impacts, eventually creating dangerous clouds of debris.

He warned space junk would eventually form faster than the rate at which it de-orbits, leaving Earth surrounded by permanent belts of debris, a scenario now known as the Kessler syndrome.

Mason says by some estimates Kessler syndrome is already a reality.

"The collision between the Iridium 33 and Cosmos 2251 satellites in 2009, created a debris cloud of two to three thousand pieces," he says.

"Two years earlier, the Chinese blew up the Fengyun 1C spacecraft using a missile, also leaving a huge debris field, which over time spread out to eventually envelope the whole Earth."

Mason says debris from these two incidents alone increased the amount of junk in space by about 20 per cent.

"The more debris the higher the probability of another collision."

Mason is concerned this will eventually collide with spacecraft.

"The space shuttle was hit by nothing more than a paint fleck, but it left a crater in the windscreen," he says. "Imagine what a chunk of satellite would do."

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