The four newcomers — representing the US, Japan and Russia — will spend the next few days learning the station’s ins and outs from Butch Wilmore and Sunita Williams. Then the two will strap into their own SpaceX capsule later this week,

Butch Wilmore and Sunita Williams expected to be gone just a week when they launched on Boeing's first astronaut flight. They hit the nine-month mark earlier this month

The arrival of the new crew will pave the way for the return of two astronauts who have been "stuck" on the station since June of last year.