Tuesday, May 19, 2015

International Space Station Might Shoot Space Junk With Laser

International Space Station could use a laser to shoot down space junk. Credit: NASA (laser added by Brevard Times).

CAPE CANAVERAL, Florida -- Scientists have come up with a solution to get rid of space junk in low Earth orbit by detecting it with a telescope and then shooting the debris with a laser mounted on the International Space Station (ISS).

But don't look forward to any laser-induced explosions is space. After locating a piece of floating space junk with a super-wide field-of-view telescope, scientists propose shooting the debris with a laser pulse to slow down its orbit; thereby causing the space junk to fall back into Earth's atmosphere.

Space junk is made up of artificial objects orbiting the Earth as a result of human activities. The number of objects have nearly doubled from 2000 to 2014 and pose a hazard to present and future space activities. Recent estimates place the total mass of space junk to be about 3,000 tons.  Because the debris exists in different orbits, it is difficult to find and capture. 

The EUSO telescope, which would be used to find the space junk, was originally planned to detect ultraviolet light emitted from air showers produced by ultra-high energy cosmic rays entering the atmosphere at night. “We realized,” says Toshikazu Ebisuzaki, who led the research effort, “that we could put it to another use. During twilight, thanks to EUSO’s wide field of view and powerful optics, we could adapt it to the new mission of detecting high-velocity debris in orbit near the ISS.”

The second part of the experiment, the CAN laser, was originally developed to power particle accelerators. It consists of bundles of optical fibers that act in concert to efficiently produce powerful laser pulses. It achieves both high power and a high repetition rate.

Scientists say that these two instruments would be capable of tracking down and de-orbiting the most dangerous space debris, around the size of one centimeter. The intense laser beam focused on the debris will produce high-velocity plasma ablation, and the reaction force will reduce its orbital velocity, leading to its reentry into the earth's atmosphere.

The group plans to deploy a small proof-of-concept experiment on the ISS, with a small, 20-centimeter version of the EUSO telescope and a laser with 100 fibers. “If that goes well,” says Ebisuzaki, “we plan to install a full-scale version on the ISS, incorporating a three-meter telescope and a laser with 10,000 fibers, giving it the ability to deorbit debris with a range of approximately 100 kilometers. Looking further to the future, we could create a free-flyer mission and put it into a polar orbit at an altitude near 800 kilometers, where the greatest concentration of debris is found.”

“Our proposal is radically different from the more conventional approach that is ground based, and we believe it is a more manageable approach that will be accurate, fast, and cheap," said Ebisuzaki. "We may finally have a way to stop the headache of rapidly growing space debris that endangers space activities. We believe that this dedicated system could remove most of the centimeter-sized debris within five years of operation.”

The scientific team's research and proposal was published in the most recent edition of Acta Astronautica.