The launch involves a brand new Falcon 9 booster, which will be expended -- not recovered -- after lift-off, due to Air Force requirements. The satellite will be deployed to medium Earth orbit just under two hours after lift-off, and while local Air Force forecasters put the weather at 90 percent "go" for the attempt today, the company had already bookmarked a backup launch window for tomorrow, December 19th, just in case. Watch the launch live using the player below or at spacex.com/webcast.

Update 12/18/2018 9:39AM ET: SpaceX has pushed the launch until tomorrow morning "due to an out of family reading on first stage sensors." However, the company says the "vehicle and payload remain healthy" for another attempt at 9:07AM ET tomorrow. This post has been updated to reflect these developments.