The four newcomers — representing the U.S., Japan and Russia — will spend the next few days learning the station’s ins and outs from Butch Wilmore and Suni Williams. Then the two will strap into their own SpaceX capsule later this week to close out an unexpected extended mission that began last June.

The replacements for NASA’s two stuck astronauts launched to the International Space Station on Friday night, paving the way for the pair’s return after nine long months. Butch Wilmore and Suni Williams need SpaceX to get this relief team to the space station before they can check out.

SpaceX's Falcon 9 rocket lifted off at 7:03 p.m. ET (2303 GMT) from NASA's Kennedy Space Center in Florida carrying four astronauts who will replace Wilmore and Williams, both of whom are veteran NASA astronauts and retired U.