A US rocket technology expert says the re-entry vehicle of the North Korean ballistic missile launched last week likely disintegrated after re-entering the atmosphere.
North Korea says it successfully test-fired its 2nd intercontinental ballistic missile on Friday.
Michael Elleman, a member of a research group at Johns Hopkins University, analyzed video captured by NHK cameras in the northernmost Japanese prefecture of Hokkaido.
The NHK footage shows a flash of light from an apparent missile re-entry vehicle off western Hokkaido in the Sea of Japan shortly after midnight on Saturday.
Elleman released a report on Monday saying that it was a re-entry vehicle, or RV.
The report says frictional forces of re-entry into the earth's atmosphere caused the RV to glow at about 20 kilometers above sea level. It says the vehicle then appeared to shed small radiant objects for about 4 seconds before dimming and disappearing at an altitude of 3 to 4 kilometers.
Elleman says the footage indicates the RV disintegrated about the time it experienced maximum stressing loads.
The report concludes that if his assessment is accurate, North Korea's engineers have yet to master re-entry technologies, and work remains before they have an ICBM capable of striking the US mainland.