The International Space Station has been understaffed for nearly three weeks ever since NASA rushed home four astronauts after one of them experienced a health issue.

The medical evacuation of Crew-11 – an unprecedented move in the space station’s 25-year history – left the orbital laboratory with just three astronauts on board to keep the station humming along. But reinforcements are set to be on the way in the days ahead after NASA elected to move up the launch date for a mission with SpaceX known as Crew-12.

The four astronauts selected for the mission, including two Americans, will then spend the next six months or so performing science experiments and conducting routine maintenance on the orbital outpost.

But another upcoming crewed mission, the space agency’s historic Artemis 2 spaceflight around the moon, could create a logistical challenge for NASA as it prepares for two seperate human spaceflights at the same time.

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Firefly’s Blue Ghost lunar lander captures its shadow on the moon’s surface after completing a successful landing March 2 near a volcanic feature on the moon called Mons Latreille. The vehicle became the first of two landers manufactured by a U.S. company to reach the moon is 2025 in crucial missions to lay the groundwork for NASA to return humans to the lunar surface in the years ahead.

Here’s everything to know about the Crew-12 launch date, as well as the astronauts selected for the mission.

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When will Crew-12 launch? NASA moves date up

The Crew-12 mission, originally slated for no earlier than Feb. 15, could now get off the ground as early as 6 a.m. ET, Wednesday, Feb. 11, according to NASA.

SpaceX uses its Falcon 9 rocket – one of the most active in the world – to launch the crew missions in Florida, typically from NASA’s Kennedy Space Center. 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.

Because four different astronauts are due to launch from the Kennedy Space Center on the Artemis 2 lunar mission around the same time, Crew-12 will instead lift off from the neighboring Cape Canaveral Space Force Base.

Artemis lunar mission launch date could delay Crew-12

But here’s where things get complicated.

The fate of the Crew-12 launch is intertwined with the impending launch of the Artemis 2 mission. Because the Artemis 2 launch window could brush up against a target liftoff of Crew-12, just when the mission can get off the ground hinges on the timing of the lunar venture.

The four astronauts selected for Artemis 2 – NASA astronauts Reid Wiseman, Victor Glover, Christina Koch and Canadian Space Agency astronaut Jeremy Hansen – are due for a 10-day trip around the moon in the first human lunar mission in more than five decades. The objective of the spaceflight is to set the stage for a future lunar landing during Artemis 3.

It’s a delicate dance for NASA, but because Artemis 2 is one of the most significant missions for NASA in half-a-century, that mission is the priority.

Additional launch opportunities for Crew-12 are on Feb. 12 and 13, according to NASA. But if Artemis 2 were to launch Sunday, Feb. 8 – its earliest launch opportunity – NASA officials said they will wait until Feb. 19 for Crew-12 to get off the ground, which would be after the Artemis 2 astronauts return.

“We will work around Artemis in all those scenarios,” Steve Stich, manager of NASA’s Commercial Crew Program, said at a Friday, Jan. 30 press conference. “So, it depends,”

What is the SpaceX Crew-12 mission?

As the name suggests, Crew-12 will be NASA and SpaceX’s 12th human science expedition to the International Space Station.

The missions, most of which last about six months, are contracted under NASA’s commercial crew program. The program allows the space agency to pay SpaceX to launch and transport astronauts and cargo to orbit aboard the company’s own 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.

Why did Crew-11 return to Earth early? What to know about medical evacuation

The accelerated launch of Crew-12 became necessary when NASA medically evacuated the four Crew-11 astronauts Jan. 15 after one them experienced a health issue.

Neither NASA nor the astronauts themselves have disclosed the name of the crew member or the nature of the medical concern that prompted the early end to the mission.

The crew members – NASA astronauts Zena Cardman and Mike Fincke, Japanese astronaut Kimiya Yui of the Japan Aerospace Exploration Agency (JAXA) and Russian cosmonaut Oleg Platonov – landed safely off the coast of California near San Diego.

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NASA’s Hubble Space Telescope last observed come 3I/ATLAS on Nov. 30, about four months after Hubble’s first look at the interstellar comet. 3I/ATLAS became one of the biggest cosmic stories of the year when astronomers deemed it to be the third-ever discovered interstellar object in our solar system originating from an entirely different part of the galaxy.

What astronauts are on the Crew-12 mission?The four members of NASA’s SpaceX Crew-12 mission to the International Space Station pose together for a crew portrait inside a SpaceX Dragon spacecraft. From left are, Roscosmos cosmonaut Andrey Fedyaev, NASA astronauts Jack Hathaway and Jessica Meir, and ESA (European Space Agency) astronaut Sophie Adenot.

The four members of NASA’s SpaceX Crew-12 mission to the International Space Station pose together for a crew portrait inside a SpaceX Dragon spacecraft. From left are, Roscosmos cosmonaut Andrey Fedyaev, NASA astronauts Jack Hathaway and Jessica Meir, and ESA (European Space Agency) astronaut Sophie Adenot.

The Crew-12 mission is composed of a contingent of four international astronauts, including two Americans.

Here’s a look at the crew:

Mission commander Jessica Meir, a marine biologist from Maine who was selected as a NASA astronaut in 2013 and is making her second trip to the space station;

Pilot Jack Hathaway, a Navy pilot from Connecticut who is making his first spaceflight after he was selected as part of the 2021 NASA astronaut class;

Mission specialist Sophie Adenot, an astronaut with the European Space Agency from France making her first spaceflight;

Mission specialist Andrey Fedyaev, a cosmonaut with Russia’s Roscosmos space agency making his second flight to the ISS.

What astronauts are on the International Space Station?

A skeleton crew of just three astronauts are 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 also the newest additions at the orbital laboratory.

Contributing: Rick Neale, Florida Today

Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@gannett.com

This article originally appeared on USA TODAY: SpaceX Crew-12 launch date moved by NASA after medical evacuation