Four astronauts are hours away from strapping into a spacecraft and departing the International Space Station about a month early after one of them experienced a health issue. The impending departure would mark the first time in the station's 25-year history that a crew on the orbital outpost has cut a mission short in order to be medically evacuated.

NASA and SpaceX are targeting no earlier than 5:05 p.m. EST, Wednesday, Jan. 14, for the undocking of the agency’s SpaceX Crew-11 mission.

On Thursday, a pair of astronauts will venture outside the space station to prepare for the future installation of roll-out solar arrays that will help power its deorbit in 2030.

Four space station Crew 11 fliers splashed down off the Southern California coast at 3:41 a.m. ET, closing out a 167-day stay in space cut short by a medical issue.