Even the final frontier is getting crowded these days, as illustrated by the 2009 smashup of an American communications satellite with a Russian one. The U.S. is currently tracking space objects with an outmoded system commissioned in 1961. But that will start to change in September when crews on Kwajalein Island in the northern Pacific start construction of the first radar site in the new $3.5 billion Space Fence network. The system uses high-frequency radar to detect objects as small as a softball at a distance of 1200 miles and can perform "uncued tracking," which means it can track objects it hasn't already registered. The result: Once it's up, the Space Fence will keep tabs on more than 200,000 objects in low- and medium-Earth orbit.