Video ,United Launch Alliance Delta 4 rocket carrying the NROL-45

(Launch webcast begins at 3:19 a.m. local (6:19 a.m. EST; 1119 GMT)

Mission Status Center

Live coverage of the United Launch Alliance Delta 4 rocket carrying the NROL-45 payload for the National Reconnaissance Office. Text updates will appear automatically below; there is no need to reload the page. Follow us on Twitter.

0409 GMT (8:09 p.m. local)The 32-story-tall mobile service tower is being retracted from the Delta 4 rocket at Vandenberg's Space Launch Complex 6 pad for today's flight that will place a surveillance satellite into orbit for the U.S. National Reconnaissance Office.

The wheeled structure, a modified piece of hardware from the pad's history as a manned launch site, is moving along rail tracks to its retracted position east of the rocket.

The 13-million-pound gantry shielded the Delta from the elements during the stay on the pad since July, provided workers 360-degree access to the various areas on the vehicle and was instrumental in attaching the strap-on solid motors and the payload during the launch campaign.

Crews will spend the next couple of hours securing the complex for launch before leaving the danger area around the pad. All workers must be clear of the area for the start of hazardous operations in the countdown, which include fueling the vehicle later tonight.

Liftoff remains scheduled for 3:39 a.m. local. The actual length of the day's available launch window to get the rocket airborne today is not disclosed to the public.

TUESDAY, FEBRUARY 9, 2016 Ready to support the national security needs of the country, a Delta 4 rocket is poised for liftoff early Wednesday from California to deliver a classified payload into space.

Liftoff from Vandenberg Air Force Base of the United Launch Alliance rocket is planned for 3:39 a.m. local (6:39 a.m. EST; 1139 GMT).

"Things are looking really great. I was down at the pad this morning, giving the rocket one last look. The weather looks great, we had a beautiful weekend, the weather is great today and the forecast for (Wednesday) is looking really well," Lt. Col. Eric Zarybnisky, 4th Space Launch Squadron commander, said in a telephone interview from Vandenberg on Monday.

"Our final closeout activities are going on today and tomorrow, kind of the normal flow as we pull some of those remove-before-flight pins and items. We've already moved the mobile assembly shelter out of the way. That was done late last week," he added.

This will be the 31st Delta 4 rocket launch since debuting in 2002 and the sixth to fly from Vandenberg.

It's hard to say it is just another Delta. Every rocket is unique. There's a lot of intricacies built in. Each of the missions have their own unique flavor. And there's a lot of folks who come together to make the mission happen. It is hard to say it is just another rocket, because it is rocket science at the end of the day," Zarybnisky said.

The two-stage rocket was rolled from the Horizontal Integration Facility to the pad in July to be hydraulically raised into the vertical position atop the launch table.

A full countdown dress rehearsal and fueling exercise occurred in early November.

The payload, already encapsulated in the rocket's 5-meter nose cone, was lifted from the payload processing facility at Space Launch Complex 6 and transported the short distance to the rocket for mating in mid-January.

Countdown activities will get underway Tuesday evening with retraction of the mobile service gantry and the start of fueling operations that will continue into the early morning of Wednesday.

"This launch will deliver a vital capability to our warfighters and our nation," said Zarybnisky, who will serve as the Air Force launch director.

"There really is no day without space. Launch is the gateway to that high ground. We stress that to our folks every day that hey, this isn’t just another launch. Each one of them is drastically important."

MONDAY, FEBRUARY 8, 2016 PREVIEW: Beginning the National Reconnaissance Office's campaign of four launches in 2016 using boosters big and small to deploy a varied collection of new intelligence satellites, a Delta 4 rocket stands ready for liftoff before sun-up Wednesday from California.

SUNDAY, FEBRUARY 7, 2016 PREVIEW: It was 1986 and the U.S. Air Force was on the cusp of something unprecedented in human spaceflight -- launching a space shuttle crew from California and paving the way for people to fly true polar missions.

http://spaceflightnow.com