The crew of NASA’s SpaceX Crew-11 mission is preparing to undock from the International Space Station on Wednesday and splash down in the Pacific Ocean a day later, marking the agency’s first-ever medical evacuation from orbit.

NASA said on Friday that the agency and SpaceX are targeting undocking no earlier than 5 p.m. ET (2200 GMT) on Wednesday, January 14, subject to weather and recovery conditions.

“Mission managers continue monitoring conditions in the recovery area, as undocking of the SpaceX Dragon depends on spacecraft readiness, recovery team readiness, weather, sea states and other factors,” NASA said in a statement. “NASA and SpaceX will select a specific splashdown time and location closer to the Crew-11 spacecraft undocking.”

The return comes after NASA earlier flagged a “medical concern” involving an astronaut aboard the ISS, prompting consideration of an early return.

Senior space agency officials later confirmed that a “serious medical condition” affecting one crew member led to the decision to bring all four astronauts home months ahead of schedule — the first emergency return in the orbiting laboratory’s 25-year history.