Astronauts to depart early from space station this week. When, how to watch

• Four astronauts are returning to Earth early from the International Space Station due to a medical issue with one of them.
• This marks the first time a crew has evacuated the station for a medical emergency in its 25-year history.
• The Crew-11 mission, a joint effort between NASA and SpaceX, will end ahead of schedule.

Four astronauts aboard the International Space Station recently began packing their bags to prepare for an unprecedented early departure to Earth after one of them experienced a medical issue.

The impending medical evacuation would bring to an untimely end a joint NASA and SpaceX mission known as Crew-11, which reached the orbital laboratory in August. When the four spacefarers on the mission, including two Americans, land back on Earth, they'll become the first crew to ever depart the space station early for medical reasons in its 25-year history.

NASA made the decision Thursday, Jan. 8, to end the mission early after one of the astronauts aboard the ISS experienced what the U.S. space agency referred to as "medical concern." The issue also prompted NASA to cancel the first of two planned spacewalks for January.

Here's everything to know about what happened on the International Space Station, and how to watch the four astronauts return home.

When will astronauts leave International Space Station early?

The astronauts of the Crew-11 mission are due to depart no earlier than 5 p.m. ET Wednesday, Jan. 14, from the International Space Station, NASA announced. Were the undocking to occur as scheduled, the crew would face a more-than 10-hour journey through space and Earth's atmosphere, culminating in a water landing around 3:40 a.m. ET Thursday, Jan. 15, off the coast of California.

"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 Jan. 9 blog post.

1st-ever ISS evacuation due to medical emergency

NASA's decision to cut short the mission came after a "medical concern with a crew member." NASA did not identify the astronaut – who is stable – nor share details about the medical issue, citing privacy.

"The capability to diagnose and treat this properly does not live on the International Space Station," NASA Administrator Jared Isaacman said in a Jan. 8 press conference.

The medical issue forced NASA to postpone a spacewalk initially scheduled for Thursday, Jan. 8. A second spacewalk set for Thursday, Jan. 15 also appears to have been canceled.

What is the International Space Station?

The International Space Station has been stationed in low-Earth orbit for more than 25 years, typically about 260 miles high, where it has been home to astronauts from all over the world. Throughout its lifespan, the station has served as a test bed for scientific research in microgravity and has in years past opened itself up to private commercial missions.

The orbital laboratory is operated through a global partnership of space agencies, including NASA, Roscosmos, the European Space Agency, the Japan Aerospace Exploration Agency and the Canadian Space Agency.

More than 290 spacefarers from 26 countries have visited the International Space Station, including 170 from the United States alone, according to NASA.

How to watch NASA coverage

NASA will provide live coverage of the return of the astronauts, beginning with them boarding and undocking on the SpaceX Dragon capsule they rode to the station until they splash down in the Pacific Ocean.

Coverage will be available on the agency's streaming app, NASA+ – also available on YouTube and the agency’s X account – as well as Amazon Prime. Netflix, which provides some live NASA coverage, including rocket launches, is not promoting the event on its platform.

What is NASA SpaceX Crew-11? When did it reach the space station?

As the name suggests, Crew-11 is NASA and SpaceX's 11th science expedition to the International Space Station.

The four astronauts selected for the mission reached the orbital laboratory in August, replacing the Crew-10 contingent.

The missions, most of which last about six months, are contracted under NASA's commercial crew program. The program allows the U.S. space agency to pay SpaceX to launch and transport astronauts and cargo to orbit aboard the company's Dragon vehicles, freeing up NASA to focus on its Artemis lunar program and other spaceflight missions, including future crewed voyages to Mars.

NASA is also hoping to certify Boeing's Starliner capsule to add a second operational vehicle for missions to the ISS before the station is retired by 2030.

Who are the astronauts on Crew-11?

Here's a look at the four astronauts who are part of Crew-11:

• Zena Cardman, a NASA astronaut from Virginia making her first spaceflight;
• Mike Fincke,  a NASA astronaut from Pennsylvania making his fourth trip to space;
• Kimiya Yui, a Japanese astronaut of the Japan Aerospace Exploration Agency (JAXA);
• Oleg Platonov, a Russian Roscosmos cosmonaut.

When will Crew-12 launch, reach space station?

The early return of the Crew-11 astronauts would leave the space station understaffed until the arrival of the mission's Crew-12 replacements.

The Crew-12 astronauts are due to arrive at the station as early as Feb. 15, NASA said as recently as Nov. 20 in a blog post. However NASA and SpaceX are now evaluating earlier launch opportunities.

SpaceX uses its Falcon 9 rocket – one of the most active in the world – to launch the crew missions from Launch Complex 39A at NASA’s Kennedy Space Center in Cape Canaveral, Florida. The astronauts themselves ride a Dragon crew capsule – the only U.S. spacecraft capable of carrying astronauts to and from the space station – that separates from the rocket in orbit.

What astronauts are on the International Space Station?

The Crew-11 astronauts are among seven people living and working aboard the International Space Station.

NASA astronaut Chris Williams and Russians Sergey Mikaev and Sergey Kud-Sverchkov, who arrived at the end of November on a Soyuz MS-28 spacecraft, are the newest additions at the orbital laboratory.

Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at [email protected]