The clandestine cargo carried into polar orbit Thursday aboard the first California-launched Delta 4-Heavy rocket was a crucial replacement satellite for the nation's surveillance and security network, amateur sky-watchers say.The sophisticated imaging bird follows a long line of Keyhole-type spacecraft that provide ultra-high resolution imagery for the U.S. intelligence community, according to hobbyists who track orbiting satellites with remarkable precision. Ever since the Delta 4-Heavy rocket fired away from Space Launch Complex 6 at Vandenberg Air Force Base, the amateur observers have been hunting for the new satellite to figure out its identity. The conventional wisdom before the launch said...