Two NASA astronauts, a Japanese flier and a Russian cosmonaut plunged back to Earth Saturday, safely splashing down in the Pacific Ocean near San Diego to wrap up a five-month mission.

A top secret payload developed in secrecy for the U.S. government is set to ride into orbit from Florida’s Space Coast aboard a SpaceX Falcon 9 rocket Thursday.

SpaceX test-fired a previously-flown Falcon 9 rocket Monday evening on pad 39A at NASA’s Kennedy Space Center in Florida, setting the stage for a launch later this week carrying the Japanese-built, Qatari-owned Es’hail 2 communications satellite to orbit.