It is so secret...even i know about it....double secret satellite?
If ya know about it, please share.
Btw, Vandenberg is required to advise/warn in advance, general aviation, commercial aviation, ships at sea, etc.. So the launch date is not a big secret. But the mission can be an entirely different story.
What is secret is its orbit, capabilities and mission. There is a world wide group of amateurs who track secret satellites visually and trade sightings on the internet. Fun times.