A SpaceX crew capsule arrived at the International Space Station on Sunday, delivering the replacements for NASA’s two stuck astronauts.

The four newcomers — representing the U.S., Japan and Russia — will spend the next few days learning the station's ins and outs.

The U.S. space agency and SpaceX are on a mission to bring home astronauts Butch Wilmore and Suni Williams. They have been stuck on the International Space Station for nine months.