NASA and SpaceX halted the countdown late Thursday for the launch of four astronauts to the International Space Station.

Mission managers rescheduled the liftoff for early Saturday morning, giving them an extra 24 hours to close out lingering issues, officials said. Nearly ideal weather was expected.

The four astronauts, representing four countries, had not yet headed to the SpaceX Falcon rocket awaiting them on the pad.

They are expected to spend six months at the space station, replacing four astronauts who have been there for half a year. A NASA astronaut is leading the new crew, which includes a Japanese surgeon and Danish and Russian engineers.

Earlier Thursday, the station had to dodge a piece of space junk, just hours before a Russian supply ship showed up with a fresh delivery. The debris, a fragment from China’s 2007 anti-satellite missile test, would have passed dangerously close if the station’s orbit not been lowered.