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Defying gravity: partnership to track space junk.

Early in the movie Gravity, a Russian antisatellite missile test unleashes a cloud of debris that shreds the International Space Station. This is just what a new business partnership hopes to avoid. Lockheed Martin and Australia's Electro Optic Systems are creating a monitoring system to track the trajectories of space junk.

The partners will use the information to forecast kely collisions, giving satellites (as well as the ISS) enough time to change their orbits to get out of the way.

This may sound far-fetched, but EOS argues that on average, space debris knocks out about one satellite every year. Those satellites can easily cost hundreds of millions of dollars to build and deploy.

No one is certain exactly how much junk is circling the Earth. In addition to collision residue, a major source of debris was the explosion of propellant and high-pressure liquids in old launch vehicles and derelict satellites. Smaller fragments come from solid fuel effluent, debris released during missions, and even flecks of paint that pop off rockets because of thermal stress.

In fact, the scenario played out in Gravity has parallels in an actual incident. In 2007, China tested an antisatellite missile by blowing up its own 1-ton Fengyun-1C weather satellite. This produced a large debris cloud: According to a 2007 NASA Orbital Debris Program Office estimate, it included 2,317 pieces large enough for NASA to track and more than 35,000 pieces larger than 1 centimeter.

While a swarm of dime-sized particles may not sound threatening, each fragment is moving at 14,000 miles per hour and packs a huge kinetic wallop. In 2013, a Fengyun fragment apparently disabled a Russian scientific satellite. Due to slight variations in their trajectories, the fragments in the Fengyun swarm continue to spread over a wider area, making future collisions more likely.

This is just one of many orbital collisions. In 2009, a derelict Russian Kosmos satellite rammed an Iridium communications satellite 500 miles above Siberia and created a large debris cloud. Earlier, in 1996, fragments of an exploded Ariane booster rocket took down a French microsatellite.

Space junk has also given astronauts a scare. In 1996, for example, a piece of debris penetrated halfway through the front window of the space shuttle Endeavour and threatened its integrity during reentry. In 2006, a piece of circuit board sliced into Atlantis's cargo bay. At least three times, astronauts evacuated from the International Space Station to their rescue craft when they received late warnings about approaching debris.

NASA routinely tracks more than 21,000 pieces of debris larger than 10 cm using a combination of optical telescopes and radar. It estimates there are 500,000 fragments between 1 cm and 10 cm in size.

Lockheed Martin estimates there are hundreds of thousands of fragments larger than 5 cm. It plans to track 200,000 of them with the Space Fence S-band radar system it is building for the U.S. Air Force.

"These radar-based systems are very good for scanning large portions of sky and giving you a wide-angle view of what's out there so we can catalog and track it," Lockheed Martin spokesperson Matt Kramer explained.

"The laser ranging system we are building with Electro Optic Systems will zoom in closely on specific objects in those swarms and tell you exactly where they are, how fast they are moving, and what they are made of. This will let us make precise projections of the path of that debris.

"We're going to sell that information, first to the government and then private industry. They can use the information to make very precise decisions about whether or not to move their satellite out of the way. That's important, because satellite propellant is a very precious resource, and once you run out, there is no way to refill the tank," Kramer said.

The companies plan to start building their laser facility in Australia this year and finish by early 2016. By cataloging space debris, they hope to make space--and the ISS--safer for both astronauts and satellites.
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Author:Brown, Alan S.
Publication:Mechanical Engineering-CIME
Date:Nov 1, 2014
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