There doesn't seem to be any official word from U.S. defense officials online yet, but if North Korea is preparing for another missile launch, then the Ground-based Midcourse Defense System of ballistic interceptors based in Alaska and California probably is on alert.
The New York Times is reporting that North Korea said today it was preparing to send a satellite into orbit in what U.S. and South Korean officials believe will be a provocative test of a long-range missile capable of reaching parts of North America. CNN is reporting it too.
A statement from Pyongyang, via the official Korea Central News Agency online, also said today that "preparations for launching experimental communications satellite Kwangmyongsong-2 by means of delivery rocket Unha-2 are now making brisk headway at Tonghae Satellite Launching Ground in Hwadae County, North Hamgyong Province."
The statement said North Korea "envisages launching practical satellites for communications, prospecting of natural resources and weather forecast, etc. essential for the economic development of the country in a few years to come and putting their operation on a normal footing at the first phase of the state long-term plan for space development."
The move comes as U.S. and South Korean officials warned the enigmatic North in recent days not to do so. "We have made it clear that we consider it both provocative and unhelpful," Secretary of State Hillary Clinton said. "And we will continue to seek ways to discourage them from launching a missile for any purpose."
U.S. officials declared themselves pleasantly surprised with GMD when they placed it on an extended, 40-day alert in mid-2006 ahead of North Korea's infamous July 4 ballistic missile tests. The alert provided an effective shakedown of the system and allowed the team to work out bugs that could not have been discovered any other way, GMD prime Boeing and Missile Defense Agency officials said through 2007.
North Korea test launched a number of missiles that day including a long-range Taepodong-2 that might have been capable of reaching some non-continental U.S. states and territories. All splashed down harmlessly in the Sea of Japan, and in fact may have fizzled quickly.
As Aviation Week reported in mid-2007, those launches, as well as ballistic missile demonstrations by Iran, have driven U.S. officials to make plans for simultaneously operating and testing their defenses, which include radars in the U.S., Europe and Pacific region, space-based detectors and interceptors at Ft. Greely, Alaska, and Vandenberg AFB, Calif.
BBC has an excellent wrap-up of North Korea missile mania too.