NROL-91 mission set to take off from Vandenberg Space Force Base on Saturday

VANDENBERG, Calif. – Officials at the Vandenberg Space Force Base are preparing for the Saturday launch of a ULA Delta IV Heavy carrying the NROL-91 mission for the National Reconnaissance Office.

The rocket is set to lift off from Space Launch Complex-6 at the space force base on Saturday at 2:53 p.m.

The Delta IV Heavy rocket – a heavy-lift launch vehicle –is the largest type of the Delta IV family and one of the world's most powerful rockets, officials said. It has had 13 successful launches and is the world's second-highest payload weight capacity rocket in operation.

The forecast on Thursday showed a 90% chance of favorable weather conditions for the launch, according to Space Force Base officials.

Officials' primary concern is thick clouds and lift-off winds, which could constitute a 24-hour delay.