Three RC-135S Cobra Balls were airborne during launch of Hwasong-15
The Omaha World-Herald reports that three RC-135S Cobra Ball spy planes were airborne during the time North Korea test-fired the Hwasong-15 intercontinental ballistic missile.
By U.S. Air Force [Public domain], via Wikimedia Commons
The Cobra Ball is equipped with special electro-optical instruments designed to observe ballistic missile flights at long range.
Read more here:: Alert5 (Air)