Tokyo’s Riken institute has proposed that a telescope with a mounted laser on the International Space Station (ISS) could be used to track, and then zap, small bits of space junk.
As designed, the system could be used on space debris a mere centimeter in size. They’re big enough to do damage, but too tiny to track from earth and evade in orbit.
(Very good 2013 ESA video on space debris)
The EUSO telescope, which will be used to find debris, 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 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.
The new method combining these two instruments will be capable of tracking down and deorbiting 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.”
In his 1978 novel The Fountains of Paradise, Arthur C. Clarke makes exactly this suggestion; he calls it Operation Cleanup.
Fortunately, the old orbital forts were superbly equipped for this task. Their radars - designed to locate oncoming missles at extreme ranges with no advance warning - could easily pinpoint the debris of the early Space Age. Then their lasers vaporized the smaller satellites, while the larger ones were nudged into higher and harmless orbits.