Building an Electronic Fence to Track Space Junk

To ward off orbital debris, three aerospace companies compete to design a "space fence"

Space Junk

An artist's impression of space debris in low-Earth orbit. The U.S. government wants a better surveillance system to keep track of the thousands of space junk pieces.ESA

Thousands of manmade pieces of space junk orbit the Earth, threatening astronauts and unmanned missions alike. Now the U.S. Air Force Space Command wants an electronic "space fence" that could track any orbital object larger than two inches in width.

Such a surveillance system would require a global network of sensitive S-band radar stations that operate in the gigahertz range of the electromagnetic spectrum. The U.S. Air Force currently relies on a system dating back to 1961, which only covers the continental United States, and can only track objects 20 inches in width or larger.

The growing cloud of space debris in Earth orbit includes more than 16,000 pieces of debris larger than four inches in width. And that only seems likely to grow, given incidents such as a satellite collision in February and space weapon tests by several nations involving old satellites.

A piece of space junk even forced astronauts to temporarily evacuate the space station in March as a precaution. Experts also continue to warn of the dangers to the growing numbers of private launches and space tourism.

Northrop Grumman, Lockheed-Martin, and Raytheon have each received $30 million from the U.S. government to compete in the federal "space fence" competition, which ends in 2010. And beyond that date, wilder solutions could come into play to begin helping clean up the orbital mess.

Worrywarts on Earth can ease up a bit in the meantime, too. NASA has said that our chances of being struck by a falling piece of space debris are extremely slim.