Sunday's failure of an improved version of the North Korean Taepo-Dong-2 has deprived U.S. intelligence agencies from assessing performance of the vehicle's third stage. This is deemed critical to determining the precise threat the vehicle poses as an ICBM that could attack Alaska, Hawaii or deeply into the continental U.S.

Image Atlantic Council.

Almost immaterial in the post-flight analysis is the failure of the vehicle to place a small communications satellite in low earth orbit, North Korea's stated intention.

Unlike on the previous launches of earlier versions of the long-range vehicle, the North Koreans announced the planned impact zones for the first and second stages of the vehicle to warn ships and commercial aircraft out of the area.

North Korea says the satellite launch mission succeeded, but the U.S. says the vehicle failed about half way through an about 13-minute ascent. This plunged the second and third stages, along with the satellite into the mid-Pacific Ocean.

The vehicle was heavily redesigned after its 1998 initial launch failure that succeeded in sending the second stage over Japan.

A redesigned version was launched in July 2006 and this time failed early in first stage flight.

The design was then changed again to the version launched Sunday, with liquid propellant first and second stages and a long narrow solid propellant upper stage with a short bulbous satellite shroud.

A factor lost on virtually all news media commentators in describing the vehicle following its launch is that the North Korean rocket flown is a three-stage, not a two-stage vehicle.

The U.S. was able to monitor key phases of the countdown using land, sea and air-based electronic intelligence assets. In the minutes prior to launch, the North Korean activation of its tracking radars was a tip off that the launch was imminent.

Following liftoff at 0230 GMT (10:30 p.m. EDT Saturday) the vehicle flew on essentially a 90.5-degree azimuth. The launch occurred at 11:30 a.m. local time at the North Korean Musudan-ri launch on the northeast coast of the Korean peninsula.

Radars in Japan and on U.S. and Japanese destroyers in the Sea of Japan and the western Pacific detected the launch immediately as it occurred as did two or three Defense Support Program (DSP) missile early warning spacecraft monitoring the Pacific region. The DSPs likely also detected the fiery reentry and breakup of the vehicle over the west-central Pacific several minutes later.

The first stage burned as planned and fell into the Sea of Japan 280 kilometers (173 miles) west of northern Japan.

Japanese navy ships were pre positioned in the area and raced to the splashdown area with the hope of recovering debris for analysis.

The second stage may have ignited, but analysts are still assessing for how long it burned. If it did ignite, the second stage did not complete its firing. As a result the vehicle impacted 1,070 kilometers (664 miles) in the Pacific off the east coast of Japan. This was several hundred miles west and short of the area that North Korea announced where the second stage and payload shroud debris would fall.

U.S. intelligence agencies are closely assessing whether the first and second stages used an up-rated rocket engine compared with the previous two launches.

The third stage has not yet been tested in flight, a key objective for both North Korean success and U.S. analysis of the rocket's capabilities.

"Once they are successful with a third stage they would have a missile that could reach the western U.S.," according to Rep. Jane Harmon (D-Calif.), chairwoman of the House Homeland Security Subcommittee On Intelligence and Risk Assessment. "This is very serious and so it is critical that this administration play keen attention to this test activity," she said in a recent NBC interview.

The solid propellant upper stage resembles that used on the U.S. Thor-Able rocket design flown in the early 1960s.

The North Korean stage would have accelerated the payload to 17,500 mph velocity for the orbital mission or a targeted slower velocity cutoff for ICBM missions to North America.

Light-weight variations of the TD-2 with an advanced third stage could fly as far as 15,000 kilometers (9,315 miles) placing much of the U.S. at risk from a nuclear or biological attack if the North Koreans are able to master the miniaturization of such weapons.