Spaceflightnow reports [spaceflightnow.com] on the next launch of the SpaceX Falcon 9 Rocket:
Falcon 9 • Iridium Next 51-55 & GRACE Follow-On
Launch time: 1947:58 GMT (3:47:58 p.m. EDT; 12:47:58 p.m. PDT)
Launch site: SLC-4E, Vandenberg Air Force Base, California
A SpaceX Falcon 9 rocket will launch five satellites for the Iridium next mobile communications fleet and two Gravity Recovery and Climate Experiment Follow-On (GRACE Follow-On) satellites for NASA and the German Research Centre for Geosciences (GFZ). The Falcon 9 rocket will launch with a previously-flown first stage.
As it usually does, SpaceX has a live feed page up on YouTube [youtube.com] which also notes:
A backup instantaneous launch opportunity is available on Wednesday, May 23 at 12:42 p.m. PDT, or 19:42 UTC.
[...] SpaceX will not attempt to recover Falcon 9’s first stage after launch.