Military wants to know: Whose satellites are those?

U.S. military observers can have trouble identifying satellites whizzing overheard in Earth's crowded space lanes. A new Pentagon effort aims to find the unique visual signatures of individual satellites for quick identification, regardless of whether such satellites belong to friend or foe. The Defense Advanced Research Projects Agency hopes such signatures — remotely seen from ground or space sensors — could even help identify different satellites made by the same manufacturer. But it's not easy. More

(Source: MSNBC - May 5)