BEECH 200 Super King Air 84-0151. Call sign SLICK06. Vandenburg AFB space launch complex six, sometimes referred to as Slick Six.
Space Launch Complex 6 (SLC-6, pronounced "Slick Six") at Vandenberg Space Force Base in California is a launch pad and support area. The site was originally developed for Titan III rockets and the Manned Orbiting Laboratory, but these were cancelled before construction of SLC-6 was complete. The complex was later rebuilt to serve as the west coast launch site for the Space Shuttle, but went unused due to budget, safety and political considerations. The pad was subsequently used for several Athena rocket launches before being modified to support the Delta IV launch vehicle family, which have used the pad since 2006.
https://en.wikipedia.org/wiki/Vandenberg_Space_Launch_Complex_6