On Wednesday afternoon, a four-person astronaut crew is set to strap into a SpaceX capsule and undock from the International Space Station.
The members of NASA's Crew-11 mission are coming home about a month early because one of the crew has a health condition worrisome enough that the space agency decided the person needed to get thoroughly checked out on the ground.
NASA astronauts Zena Cardman and Mike Fincke, along with Russian cosmonaut Oleg Platonov and an astronaut from Japan named Kimiya Yui, are expected to splash down off the coast of California early Thursday morning.
This is the first medical evacuation of the International Space Station in its 25-year history. Officials have stressed it's not an emergency evacuation, as the astronaut's condition is stable. The identity of the astronaut and the nature of the problem have not been released for privacy reasons.
During a change-of-command ceremony beamed down from the orbiting outpost on Monday, all seven people on board the I.S.S. spoke on camera, and none appeared obviously ill.
"Our timing of this departure is unexpected, but what was not surprising to me was how well this crew came together as a family to help each other and just take care of each other," said Cardman, "and this includes very much our teams on the ground."
"We are all OK. Everyone on board is stable, safe, and well cared for," Fincke wrote in a social media post, saying that coming home early was "the right call, even if it's a bit bittersweet."
Another NASA astronaut, Chris Williams, and two Russian cosmonauts will remain on board the station. A replacement four-person crew is scheduled to launch in a SpaceX capsule in February.
NASA trains crews for medical emergencies and even has considered what to do if an astronaut dies in orbit.
Previously, space station officials had predicted that they might have to bring an astronaut home early for health reasons as often as once every three years or so during the lifetime of the orbiting outpost.
"And we've not had one to date," James Polk, NASA's chief health and medical officer, noted in a press briefing.
The first public sign of the current medical issue came on Jan. 7 when NASA abruptly called off the first planned spacewalk of the year, saying the agency was "monitoring a medical concern with a crew member that arose Wednesday afternoon aboard the orbital complex." The next day, the agency announced plans to bring its Crew-11 team back early.
Polk said this situation was serious enough that the team wanted to do a full diagnostic workup on the astronaut, "and the best way to complete that work is on the ground, where we have the full suite of medical testing hardware."
It's not the first time that teams back on Earth have had to triage medical conditions in space, given that the station has been continuously inhabited for a quarter-century and astronauts can suffer from the usual routine ailments that affect mortal humans — as well as physical issues associated with unusual movements of body fluids because of microgravity.
"We've had a host of different things that we've treated on orbit," Polk said, listing health troubles like toothaches and ear pain.
They've even dealt with problems like a blood clot in an astronaut's jugular vein that was discovered accidentally, during a research study on blood circulation in space.
In that case, NASA consulted with Stephan Moll, an expert on blood clots and bleeding disorders at the University of North Carolina at Chapel Hill. He says a clot in this vein is uncommon on the ground, to say nothing about space, and there were a lot of unknowns; untreated, it might just resolve on its own, or it might progress to more serious complications.
Fortunately, for reasons Moll says he can't disclose, the station happened to have an injectable anti-clotting drug on board, which the astronaut took until pills could be sent up on a resupply mission.
Injecting the drug in space wasn't easy, however, as microgravity turned the liquid in the vial into floating drops that had to be hunted down with the needle. "In space, it took about twenty minutes for the astronaut, initially, to fill one syringe," he says, so it was quite cumbersome but doable.
Moll says he was really struck by the professionalism of the whole NASA team in working through this conundrum. "I was so impressed how detailed-oriented and thoughtful people are, not just assuming things," he says.
And he remembers getting a call on his home phone from the orbiting astronaut, up on the station, who wanted to talk things over with him directly.
"They're just in a different environment, but it comes down to the same concerns that other patients have," says Moll. "They're just normal people up there."
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