Laser proposed to deflect space junk

It won’t prevent Armageddon, but a simple ground-based laser system could nudge small pieces of space junk away from satellites to prevent collisions, a new study suggests.

The proposed system uses photons generated by a medium-power laser and aimed into space through a 1.5-meter telescope. The photons exert pressure on space debris in low-Earth orbit, gently pushing the objects aside rather than vaporizing them. Researchers have applied the same idea, using the pressure from sunlight, to propel spacecraft (SN: 8/21/99, p. 120).

James Mason of the Universities Space Research Association and NASA’s Ames Research Center in Mountain View, Calif., and his colleagues describe their system online at arXiv.org on March 10. The proposed device, which would cost a little over $10 million, could be ready for testing next year and fully operational a few years later.

About 500,000 pieces of space debris centimeter-sized and larger reside in low-Earth orbit. Most are fragments of abandoned spacecraft that have broken up or exploded. The number of cataloged space-debris pieces larger than 10 centimeters has risen dramatically in recent years and most satellites don’t have shielding that would protect them from collisions with such debris, says Don Kessler, a retired NASA senior scientist and orbital debris expert.

If a piece of space debris had to be moved by about 200 meters a day to avoid a collision, a medium-power laser of about 5 kilowatts could provide the needed push — provided the debris had a large surface area and was no heavier than 50 to 100 kilograms, Mason calculates.

Such a laser couldn’t have prevented a 2009 collision between two satellites (SN: 3/14/09, p. 9), nor could it push aside an asteroid. But the system ”could move light debris out of the way of a big object,” says Mason.

Mason’s team suggests that the laser facility be built at a near-polar, high-altitude site, such as the Plateau Observatory in Antarctica, because most debris passes over the polar regions many times a day.

Researchers have suggested using lasers to vaporize space debris for more than two decades, but those systems would require powerful devices that might be mistaken for weapons, notes Mason.

Using a laser to slightly alter the speed of small debris doesn’t take much energy, notes Kessler. And if the medium-power laser missed its target it would be unlikely to do much damage, he adds. Kessler notes, however, that scientists would need precise knowledge of the path of debris in order for the system to be effective.