A pair of NASA/DLR scientific spacecraft designed to study the Earth’s water cycle and how mass is distributed around the planet’s surface and subsurface, the Gravity-Recovery And Climate Experiment – Follow On (GRACE Follow On) satellites, were launched into a near polar low Earth orbit from the Vandenberg launch site in California by a SpaceX Falcon 9v1.2FT Block 4 rocket.  The launch took place at 1948 GMT on 22 May 2018. Also aboard the launch were five Iridium Next satellites of the low Earth orbit communications satellite constellation.

Given that the new Block 5 version will soon be fully replacing the Block 4 series of the Falcon 9,  the Block 4 first stag on this flight, which had been used before and had landing legs, was simply splashed down for disposal in the Pacific ocean with no attempt to land it.

Falcon 9 launch of GRACE Follow-On satellite pair and five Iridium Next spacecraft. Courtesy: SpaceX