Fiber laser plan to clear space debris

23 Apr 2015

Wide-angle telescope and high-efficiency CAN laser form "blueprint"; trial project heading for ISS to cut threats to satellites.

A Japan-led international team of scientists are proposing a "blueprint" for a space-based system to solve the growing problem of space debris, as optics.org reported last year. The proposal, published in the journal Acta Astronautica, combines a super-wide field-of-view telescope, developed by University of Riken’s EUSO team (Saitama, Japan), which will be used to detect the objects, and a recently-developed high-efficiency laser system, the CAN laser that was presented in Nature Photonics in 2013, to track space debris and remove it from orbit.

Space debris, which is continuously accumulating as a result of human space activities, consists of artificial objects orbiting the earth. The number of objects nearly doubled between 2000 to 2014 and the items have become a major obstacle to space development, say the researchers. The total mass of space debris is calculated to be about 3,000 tons today. It consists of derelict satellites, rocket bodies and parts, and small fragments produced by collisions between debris.

Growing threat

Because the debris exists in different orbits, it is difficult to capture. The objects can collide with space infrastructure such as the International Space Station (ISS) and active satellites. As a result, developing remediation technology has become a major challenge.

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.

The Acta Astronautica article states, "Equipped with 2.5 m optics and a field of view of ±30°, the EUSO telescope can also be utilised for the detection of high velocity fragmentation debris in orbit near the ISS. Further tracking, characterisation and remediation are to be performed by a CAN laser system operating in tandem with the EUSO telescope. For full scale versions of both instruments, the range of the detection/removal operation can be as large as 100 km."

“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 1cm in diameter. 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, 20cm 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 de-orbit debris with a range of approximately 100km. Looking further to the future, we could create a free-flyer mission and put it into a polar orbit at an altitude near 800km, where the greatest concentration of debris is found.”

Ebisuzaki added, “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. 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.”

About the Author

Matthew Peach is a contributing editor to optics.org.