A secret military defense satellite for the United States will head into space on Thursday aboard the most massive rocket ever launched from the California coast.
The United States' National Reconnaissance Office L-49 satellite is one of the largest payloads to be placed into a polar orbit around earth, and will serve as both an early warning platform for incoming foreign threats and to observe known hostile regions.
This flight will also mark the first space shot of the new year for the United States.
A United Launch Alliance Delta IV-Heavy rocket uses three liquid-fueled rocket boosters at launch, and will carry aloft the NROL-49 from launch pad SLC-6 at Vandenberg, AFB, on January 20 at 4:08:05 pm EST (1:08 pm local).
The brief launch window closes at 4:23 pm, Air Force officials said.
This fifth flight of a Delta IV-Heavy will lift-off from the south base's space launch complex 6, the same pad which was primed in the mid-1980's for the military's space shuttle launches.
Four previous Delta IV-Heavy's have launched from Cape Canaveral Air Force Station since January 2004.
The countdown will begin at 10:38 am EDT, on Thursday at the T-5 hour, 15 minute point.
A half-hour later, the launch team will begin fueling the liquid oxygen tanks of the common booster core. Just over an hour later, the liquid hydrogen fueling will start.
The 236-foot tall rocket features three common booster cores with a single engine, each delivering nearly 745,000 pounds of thrust at launch or 2,234,000 pounds combined.
Launch begins at T-4 seconds when the three RS-68 engines ignite and throttle to full thrust.
Once the Delta rises into the midday skies, the launch will be visible around the Los Angels region to the south as the vehicle darts south and out over the Pacific Ocean.
Just over six minutes into the launch, the three booster cores will have emptied their fuel and will be jettisoned.
The exact deployment time of the payload will not be disclosed, according to the 30th Space Wing at Vandenberg.
The next Delta IV-H is on the table to fly from Cape Canaveral in December, however two medium size Delta IV's will launch beginning this spring also from the Cape.