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